If you alter the push up slightly, cin, you'll get the desired effect. By placing your hands closer togther than you would for a normal push up you'll focus on the triceps - the largest muscle in the arm and the one that will take care of that flab. Place hands approximately 6 inches apart and perform your push up.

You can see a demo of how this is performed : Tricep Push Up

These can also be done on an incline and a decline .

HTH
Nat