Bayou,

The stomach muscles are core, and most everything else can benefit from a solid core. Forget fancy (my opinion). Basic core muscle exercises done in a few burnout sets 3-4x weekly is my approach.

In the bench press and especially squat, I use the aforementioned intra abdominal pressure to aid lifting. With a standard RAW (unequipped) 4" belt, I count on core muscles to press against the belt in a manner that increases stability-- particularly in the back, though the body as a whole is inclusive in benefiting. Even without using IAP on a belt, it still helps to have a good core. Just a practical understanding of the use of abdominal muscles to aid elsewhere in physical activity....(the core is your base for many things).