I've done Bench only competitions.. I do not have training partners, boards, bands, or chains - ALL of which play an important role in powerlifting. I WISH I had partners b/c I would hit up a board routine.. Rathern, I usually start 4-5 months out with a personalized 5x5 split, which I think is geared more for strength increases than size.
Most powerlifters aren't greatly concerned with their diet as long as they stay within their weight classes. You always want to be at the top of your weight class, obviously - so you will occassionally have to cut a few lbs prior. If you do it properly, it isnt a big deal..
I, by no means, classify myself as a powerlifter. I usually do 1-2 bench meets a year for fun..