Flat Bench? Then do some dumbell hammer curls, neg. bench press, bottom position bench press, inc & or decline bench press, St. overhead barbell or dumbell press, etc...

Squat? Slow neg. squats with a pause at the bottom. 1&1/2 rep squats (go down all the way, come back up 1/2 the way, go back down and then all the way back up). Deadlifts, partial deadlifts, stiff leggs, etc...

Let me know if any of this helps. I know it sounds strange, but the more complex the movement is, the more stabilizers it will strengthen.

Ohh, the hammers for bench...I always train hammers pretty hard when I am going heavy. When you do a hammer curl, your bic is in almost the same position as a it is in the bottom position of the bench press.