Try the smith Barbell press from time to time. Personally, I've noticed that I get a better pump in my chest with the Smith, even though I primarily do heavy dumbbell presses. Also with the smith, you don't have to stabilize much with your arms and shoulders. Plus you can go heavier with the smith because of such. I tested this out by doing shoulder's one day, then did chest the next day. Normally I get poor results if doing my shoulders the day before on regular bench, as my shoulders and arms do a lot of the work as well. Well, I tried the smith the next day and I could still go very heavy and get a great pump. For now, I just jump on the Smith for incline, every other chest workout, to go even heavier, and tend to get a better pump with it as well.
I normally stick with dumbbell pressess for chest mass, but if you are looking for a pump, and less involvement or stress on the arms and shoulders you should try the Smith sometimes, if you haven't already. Just don't get too dependent on it.
Also, try some drop sets right after going heavy, not limited to the smith, but on any of your chest exercises, you should get a great pump them.