Okay, I'v heard that driving with your legs improves ones leg drive. I'v been lifting for a few months, and when I bench press, I always feel that my feets always wants to get OFF the ground, which makes it rather imposible for me to drive with the legs.
How do your feet want to get off of the ground when you're benching? Are you trying to do a sit up or something at the same time? Im having a hard time figuring out how one would do that without making a conscious effort to do so.
Think about the guys who bench without an arch - they start kicking their legs around with a heavy weight. Maybe that is what the OP is doing?
Or perhaps he is putting his weight on his toes, rather than his heels, and this makes his feet pop out?
I bench with an arch, and during my setup, I lift my toes in my shoes to make sure I am putting my weight in my heels. Then, when I am coming off the chest, I consciously kick into my heels to get the leg drive.
try arching your back more, pulling your traps together and squeezing your lats as if you were going to bend the barbell in half. On the press, just keep your feet planted on the ground and thrust out with your pelvis but do not let it come off the bench.
As a matter of fact, before you even unrack the weight try practicing getting into position to get a feel for what your body should be doing on every lift.
On a max attempt every muscle in your body should feel like it wants to explode. This is only possible with your feet anchored to the ground.