Use a full 3-second pause on the chest. It'll make you feel like a weakling, but it'll lead to great improvements in the bottom portion of the bench press. The pause will also take away any stretch reflex.

For lack of a better term, the pause requires you to "muscle" the weight up as opposed to relying on the stretch reflex to get you to about halfway up. The paused bench press also greatly helps build technique and control of the bar.