I don't claim to be an expert, other than I've stressed and strained a lot of stuff over 40+ years of weight training and sports, and figured out from reading and trying things what works for me. I strained both of my shoulders multiple times doing heavy pressing movements, never needed surgery, but last time to the point of not being able to sleep for a couple of weeks, and not being able to raise my arm above my shoulder for 6 months.
I found external rotations helped my shoulders immensely. I do 2 sets of 15-25 reps 2 times a week, on an off day or early morning on the day I do upper body movements later in the day. Started with 2 pound dumbbells, moved up to the next size dumbbells every few months, until I got to 15 pounds and then another 5 pounds every year, until now I use 30 pound dumbbells. I have a bar support somebody gave me years ago that goes over your shoulders and holds your upper arm still.
I think it is the best thing ever for shoulder rehab. They were available from multiple suppliers 10 or 15 years ago, but now nobody seems to make them any more. Not sure why. I has worked great for me, but everybody is different, so what works for me might not work for everyone else.