This would best be a question for Eric Cressey or Mike Robertson… I’m not an expert by FAR, I’m just giving my opinion and hope some others will chime in.
Now immediately I would say that there is specific work that you can do strength that area. But what that stuff bottles down to is pretty much isolation work. Which may not be advisable at the time…
So in order to build up the supporting musculature…I think you should include a lot more pulling motions and exercises that stress your upper back.
chest supported rows
bent over rows
most of your pressing motions should be vertical as well… so overhead (military) pressing
If you’re really ball-sy, Overhead squats and one arm dumbbell overhead squats.
Also limit any chest specific work that you may be doing to a minimum. Bench press, flyes and stuff. I always found that these limited my range of motion as far as shoulder movements. You can do it but don’t let it be your biggest focus.