How should I prepare a carbon frame when I want to swap in a new bottom bracket?
If it is a press fit then it is probably a BB86.  You'll need a removal tool (Park BBT-90.3, I think) and a press.  Get a SRAM GXP press fit bottom bracket or the equivalent Shimano part, they run about $40 USD. Knock the old one out with the removal tool and a hammer, clean the inside of the shell and press in the new one.  No grease.  The shells of these bottom brackets are made of a very hard plastic that will eventually loosen and start to creak.