Protestants receive forgiveness for their post-baptismal sins in exactly the same way they received forgiveness for all their pre-baptismal sins. Upon sincere confession of their sinfulness, in prayer to God and through faith in the redemptive, finished work of Christ, God pardons them. Their conscience is cleansed as a gift of free grace, and the Christian then strives to keep that conscience clean before God. See Acts 24:16 & 2 Corinthians 1:12.
However, the question really asks how Protestants receive this forgiveness, as compared with the Catholic system of confession and absolution from sins. My opening paragraph shows the stark difference between a Catholic system which promises to deal with post-baptismal sins, and Protestants continuing to look to God, in Christ, for his promise of forgiveness to obtain till their dying days, as they continue to view sin the same way they did prior to their baptism. Nay! They view sin with increasing abhorrence as they grow in grace and Christian maturity.
You rightly said that "Protestant practices vary on this" matter of dealing with on-going sins, as there are different views. This answer seeks to give a Reformed Protestant view by (1) giving one biblical example; (2) one historic example at the Reformation; (3) quotes from modern Reformed doctrinal writings on the matter, which show the need to have a balanced view of the holiness of the Church, and Church discipline.
(1) Peter's three denials of Christ in one night:
After his baptism, Peter sinned against Christ on the night of his betrayal, despite Jesus warning him in advance that he would do that.
"No one should minimize the bravery of Peter, nor mistake his ardent
devotion. Peter's tragic discovery, however, was that for all his
determination not to deny Jesus, the flesh was helpless before the
powers of darkness, nor could what was carnal attain to things that
were spiritual... Satan prepared his sieve to sift Peter, and he hoped
utterly to destroy his faith, bringing him down to despair and
death... With all his spirit he had tried; and with all his flesh he
Nevertheless, Jesus had said beforehand, 'Simon, Simon, behold, Satan
hath desired to have you, that he may sift you as wheat: but I have
prayed for thee, that thy faith fail not: and when thou art converted
[turned around], strengthen thy brethren (Luke 22:31-32). Mark John
Metcalfe, pp 206-7
Note that all the other disciples had equally betrayed Jesus that night, by running away. They might not have denied him publicly, but at least Peter tried his hardest to remain as close as possible to Jesus as his ordeal began, for he had promised to Jesus that he would not forsake him. The others forsook him at the outset, so they were in no position to require Peter to confess to them, nor to offer him absolution! They all needed the offices of Christ as the only mediator between God and man. That Protestant view is shared by all.
(2) A Reformation example of dealing with post-baptismal sin:
"...the tensions which medieval religion deliberately induced, playing
alternately upon fear and hope: Hell was stoked, not because men lived
in perpetual dread, but precisely because they did not, and in order
to instill enough fear to drive them to the sacraments of the Church.
If they were petrified with terror, purgatory was introduced by way of
mitigation as an intermediate place where those not bad enough for
hell nor good enough for heaven might make further expiation. If this
alleviation inspired complacency, the temperature was advanced on
purgatory, and then the pressure was again relaxed through
Like everyone else in the Middle Ages [Martin Luther] knew what to do
about his plight. The Church taught that no sensible person would wait
until his deathbed to make an act of contrition and plead for grace.
From beginning to end the only secure course was to lay hold of every
help the Church had to offer: sacraments, pilgrimages, indulgences,
the intercession of the saints. Yet foolish was the man who relied
solely on the good offices of the heavenly intercessors if he had done
nothing to insure their favor!
And what better could he do than take the cowl? Men believed the end
of the world already had been postponed for the sake of the Cistercian
monks. Christ had just "bidden the angel blow his trumpet for the Last
Judgment, when the Mother of Mercy fell at the feet of her Son and
besought Him to spare awhile, 'at least for my friends of the
Cistercian Order, that they may prepare themselves.' [Ref. Coulton 1,
St. Thomas Aquinas himself declared the taking of the cowl to be
second baptism, restoring the sinner to the state of innocence which
he enjoyed when first baptized. The opinion was popular that if the
monk should sin thereafter, he was peculiarly privileged because in
his case repentance would bring restoration to the state of innocence.
Monasticism was the way par excellence to heaven. Luther knew all
It was no wonder that after a visit with his parents, sudden lightning
struck him to earth [and] he cried out to his father's saint,
patroness of miners, "St. Anne help me! I will become a monk."...
"The whole sacramental system of the Church was designed to mediate to
man God's help and favor. Particularly the sacrament of penance
afforded solace, not to saints but to sinners. This only was required
of them, that they should confess all their wrongdoing and seek
absolution. Luther endeavored unremittingly to avail himself of this
signal mercy. He confessed frequently, often daily, and for as long as
six hours on a single occasion. Every sin in order to be absolved was
to be confessed... Luther would review his entire life until the
confessor grew weary and exclaimed, "Man, God is not angry with you.
You are angry with God..." Staupitz [his confessor] said, "If you
expect Christ to forgive you, come in with something to forgive -
parricide, blasphemy, adultery - instead of all these peccadilloes."
Here I Stand Roland Bainton pp28, 33, 54
So, when Luther took over the chair of Bible, which Staupitz once held, his study of the Bible (in order to teach it) revealed to him the biblical doctrines of sin, confession and forgiveness (especially as detailed in the book of Romans) and he was liberated into the freedom that Christ's redemption achieved. Not a freedom to sin but the opposite - living to be like Jesus in holiness and obedience. The sacerdotal system of Catholicism was abandoned.
(3) Modern Reformed doctrinal writings:
One example must suffice. This is about the Protestant's view of the holiness of the Church and its discipline to maintain that holiness. It shows that belonging to the Church Christ builds is essential - there can be no free-lance Christians, with nobody to answer to, here on earth.
"...even the regenerate members are 'holy and blameless' objectively
in Christ alone and will not be subjectively complete in Christ until
their glorification. This view of 'essential holiness' stands in some
contrast with both Roman Catholic and Anabaptist/pietist alternatives.
Both tend to lodge the church's holiness in some quality inherent in
the institution or in the collective piety of its individual members.
However, Scripture locates this attribute, like the others, in the
triune God and his covenantal grace...
In contrast to the Roman Catholic paradigm of fusion, radical
Protestant movements have tended to lodge the church's holiness in the
identifiable experience of the many (regenerate believers) as opposed
to the collective identity of the one church. In the Roman Catholic
perspective, the church makes the saints, while in the radical
Protestant view, the saints make the church. This draws a sharp
contrast between the Spirit's sanctifying work within believers and
the visible means of grace... Both views, however, tend to lodge the
church's holiness within the inner condition of the church itself.
This is where we find the most striking contrast with a covenantal
ecclesiology [the Reformed position].
In a covenantal ecclesiology the church is holy because the covenant
of grace is the sphere within which the Holy Trinity gathers,
protects, and keeps a people set apart from the world...
Grounded in the proper preaching of the gospel and administration of
the sacraments, discipline holds its proper place as a mark of the
true church... This is part of the ministry of the key, taught by
Jesus in Matthew 18, where the keys of the kingdom are given to the
church's pastors." Pilgrim Theology Michael Horton, pp 404-406
Much more is explained, showing that Reformed Christians believe in the gathered church, which has nothing to do with denominations, but the work of the Holy Spirit in sanctifying repentant sinners and indwelling them to complete the good work begun in them, till Christ returns. They eagerly seek to become more and more Christ-like, for his glory, not for personal benefits. Already this answer is very long, and yet has barely scratched the surface of this deep subject, but I hope it will have outlined some important points upon which Reformed Christians have moved away from Catholic systems of confession and penance.