How to cure shoulder problems 90% of the time - By Dante of DC Training with my comments added

This method has helped me tremendously as well as a couple clients. I also believe it helped my incline press strength. I always do this before any arm, delt or chest work preceded by 1 giant set of 20 reps w 15lb dbs of side, front and rear laterals. Then rear lateral machine for another 15-20 reps followed by 7-10 second static stretches both front and rear delts.

With a large towel or broomstick or 1" PVC pipe. (I like the PVC the best, it has some flex to it, which makes this a bit forgiving until you are warmed up.
Hold it with straight arms for the entire time. Start out with it with a really wide grip (with straight arms) in front of you (on your quads) and with straight arms bring it up and overhead and then down and back to the middle of your back--STRAIGHT ARMS ALL THE WAY--this is going to be very difficult and hard the first couple times out and then will be "old hat" with time----and its going to be painful in a stretching pump kind of way, 25-50 reps.

The important part of the movement is the area overhead that is really tight--do all of this carefully/slowly---dont just whip it over and back---if your hand is slipping off the broomstick even with the widest grip, or you cant bring your arms over straight and the start bending on you, you have some serious shoulder inflexibility and need to work this hard and get up to speed (or you could just need a longer broomstick too)--again do all of these revolutions controlled and carefully--push into the stretch as you go along toward the 50 revolutions, your chest will be pushing outward and your shoulders rolling back--your shoulders are going to blow up with so much blood its going to be incredibly painfull pumpwise.

Its going to be very hard to do but try your best to move your grip inward for the next 2-4 weeks and your range of motion with shoulders will increase dramatically and any impingement and the majority of other problems should be gone in 2 weeks--also try to move your grip in as you are doing the 50 revolutions--start off with a stretching but relatively easy 10 to warm up some, then try to move your grip in even by a centimeter if you can for the next 20 revolutions and then at 30 try to move the grip in another centimeter