Couple three things:
With a barbell bench press, widen your grip on the barbell, and make sure you do not lower the barbell so that the elbows go any deeper than bench / body level;
Same principle with push-ups - widen the placement of your hands on the floor;
With both bench presses and push-ups, take care to align your hands and barbell so that they are directly aligned with the mid-point of the breast;
Also remember that you will never be able to completely remove the contribution of the anterior deltoid to any pec exercise.
Hope this helps!
Annette