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 Fortress believes there are four fundamental directions a weight must be pulled or lifted in order to build a kick-ass back. He calls it his Directional Back Training Principle and it has nothing to do with North and South.