Certainly Paul's second letter was to clarify the first and was about the rapture. However, his second letter is probably what Peter was referencing when he said Paul's letters were difficult!
Many people read over this passage and miss things:
Did you notice that in 3b the man of sin IS revealed?
Did you notice that in verses 6-8 the man of sin cannot be revealed until the power restraining him, and preventing that revealing before the proper time will have been "taken out of the way?"
Since he IS revealed in 3b, then the power restraining or holding back that revealing MUST have been "taken out of the way" in verse 3a. And the ONLY part of 3a that fits is hidden in Paul's use of "apostasia."
Then we have another puzzle: why did Paul write in verse 6: "and now you know" who or what that restraining power is. I Wonder, do YOU know?
Then we must be careful to understand the times: when John gets to chapter 19, after the marriage and supper, and gets on His white horse, WHO is left in heaven? It is written that He will come WITH His saints. In fact, He comes with ALL His saints:
1 Thessalonians 3:13
To the end he may stablish your hearts unblameable in holiness before God, even our Father, at the coming of our Lord Jesus Christ with
all his saints.
The word "all" is found in every Greek text. Just that one word defeats a posttrib rapture. You see, according to Posttrib, at the time He leaves heaven, the rapture is future.
I believe when He leaves heaven, He will leave heaven empty of saints; the pretrib raptured saints will be with Him; the Old Testament saints who will be caught up "on the last day" or at the 7th vial that ends the week will be with Him. The Two Witnesses will be With Him and finally, all the beheaded will be with Him: All the righteous EXCEPT those left in natural bodies on earth will be coming WITH Him.
So WHO IS IT that is left of the elect to gather? It is only the remnant of the Hebrews left alive in the nations of the world. Jesus will send out angels to gather ALL of "Jacob" back to Israel has He has promised them.
I find a pretrib rapture fits this scenario John writes for us much better than a posttrib rapture. Verse after verse after verse gets in the way when I think of a posttrib rapture.