The LDS church believes that Christ literally preached to the spirits of deceased persons between the time of his death and his resurrection. This is taught in Doctrine and Covenants Section 132 which is a vision that Joseph F. Smith (not to be confused with Joseph Smith; Joseph F is his nephew) had of the spirits of the dead.
12 And there were gathered together in one place an innumerable
company of the spirits of the just ...
16 They were assembled awaiting the advent of the Son of God into the
spirit world, to declare their redemption from the bands of death. ...
18 While this vast multitude waited and conversed, rejoicing in the
hour of their deliverance from the chains of death, the Son of God
appeared, declaring liberty to the captives who had been faithful;
19 And there he preached to them the everlasting gospel, the doctrine
of the resurrection and the redemption of mankind from the fall, and
from individual sins on conditions of repentance.
It goes on to clarify that Christ only preached directly to the righteous spirits and then sent those righteous spirits to preach to the unrighteous.
29 And as I wondered, my eyes were opened, and my understanding
quickened, and I perceived that the Lord went not in person among the
wicked and the disobedient who had rejected the truth, to teach them;
30 But behold, from among the righteous, he organized his forces and
appointed messengers, clothed with power and authority, and
commissioned them to go forth and carry the light of the gospel to
them that were in darkness, even to all the spirits of men; and thus
was the gospel preached to the dead.
The organized preaching of the gospel to spirits of the dead is key to the LDS doctrine of salvation for the dead.