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.
A rep is not a rep. Especially when you stretch it out 30 times longer than how it's normally done. Sounds crazy, but so are the gains you'll get from it. Check it out.