Adding banded tension to your shoulder work is guaranteed to trigger new hypertrophy gains. Just grab a couple of resistance bands and wedge them under the bench for overhead dumbbell presses.
The key is to lift the dumbbells all the way up to the top and hold them there for a couple of seconds in the contracted position of each rep.
The flye is tough at the bottom of the movement but easier at the top. To match the strength curve and build more muscle, add manual resistance at the top.