I saw this partial definition of polemics in a google search
"A polemicist is a person who attacks someone else with written or
spoken words. If you're a polemicist, you have very strong opinions,
and you're not afraid to state them — even if they hurt other people."
A quote from your linked previous question is "I now want to play offense, and give the proselytizers a taste of their own medicine." I would like to humbly advise caution. Motivation of the heart is deeply important and I suggest that there is a world of difference between desiring someone to find Christ and giving someone a taste of their own medicine.
I think we are called to defend the faith...not attack others with it. However, when an opportunity presents itself it is wise to be prepared. Therefore, of primary importance is an ever growing familiarity with the Bible. If one wishes to speak on spiritual matters with any kind of authority at all one must speak from the Scriptures. Additionally, if one wishes to study the polemic of others to build one's knowledge only a firm foundation in Scripture can separate the wheat from the chaff.
The second facet is living a life that matches the Scriptures that we speak. Too often Christians condemn others for the very same things they themselves do and this completely destroys what is spoken. A clear conscience promotes a clear polemic.
But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear:
Having a good conscience; that, whereas they speak evil of you, as of evildoers, they may be ashamed that falsely accuse your good conversation in Christ. - 1 Peter 3:15-16
Following are three links that I hope may help. The first is a site to introduce the works of Francis Schaeffer and I highly recommend reading any and everything of his that you can find.
The second site is a quick biography of Schaeffer at the Gospel Coalition and contains links to pdf's of some of his most well known works.
The third site is...well...different :-) It is a video blog site called the Bible Thumping Wingnut Network and it contains a section called the Polemics Report.