I thought these videos (by FullerFigureFullerBust) were very helpful and do a good job of illustrating some of the problems I had a few years ago when my bust size had increased, but I was still trying to follow the typical method of bra fitting involving measuring my overbust, and subtracting my underbust + 5" in order to find my size.

http://fullerfigurefullerbust......ply-silly/

http://fullerfigurefullerbust......ven-wrong/