I'm taking 2CK without having gone through peds or obgyn.
I read the sections in MTB2/3, have looked at Case Files (read ~1/4 of each then jettisoned them) and have done practice questions, but they are still my weakest by a slight margin. But I really don't care about getting ~5-10 points lower like I would have for Step 1 because I just want a prelim year, so I'll just do my best to "IQ" my way through anything I don't know.