the irony of the droopy shoulder is i have overworked upper traps, just seems to go against the whole idea of it being droopy.
i would focus on s.a. muscle, lower traps, and external rotators but im sure you already knew about those
a girl i befriended on fb recc'd these guys and they have videos
http://www.youtube.com/user/fitnessseminars
THEY WORK, ive seen amazing pictures. you do not have to activate the scalenes if your deep cervical flexors are strong enough *supposedly* also i rec doing shoulder exercises lying on your back, or figure out a way to cheat gravity