When I started my yoga asana practice I ended up uncovering some shoulder dyskinesis I hadn’t been aware of from years and years of programming. That turned into a pretty bad shoulder injury that has on the plus side taught me a lot about my body.
One thing I learned is that a lot of shoulder stuff comes from tightness of the pec minor, which now in retrospect is pretty obvious. Some things that I do that have really helped with shoulder stuff:
1) Shoulder dislocates with an aikido jo. Any rigid stick works, like a broom handle.
2) Camel pose (ustrasana), but coming into it a bit differently than is usually taught in yoga classes. Keep your knees hips width distance apart, with your toes tucked under (rather than pointed), and sit on your heels. Grab your heels with your fingers on the inside of your feet (if you were to open your hand your thumbs will be pointing directly backwards). Make sure you have good shoulder rotation here. Now lift your pelvis up while holding on to your feet, get your pelvis stacked over your knees, and think about lifting your chest to the sky. Send your breath into your upper chest for 5-7 breaths and then come out the way you came in. This really opened my pec minor.
3) Gomukhasana with arms clasped behind your back. Use a strap if you can’t get the bind (it might take a while for this rotation to open).
4) Pull-ups. Lots of pull ups. Started with dead hangs, then would do 50% of max 6x times per day 3-4 days a week. Would retest max every 3 weeks. Got myself to about 15 per set before I decided I didn’t need to do that many pull ups.
5) cat cow with wrists flipped, fingers pointed backwards. Really focusing on the shoulder rotation and getting straight arm scapular engagement.
6) Infraspinatus strengthening a few times per week with light weight. Exercises were described in this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655748/
7) Lots of side planks (vasisthasana). Be careful with this one, it can do a lot of harm if you go too hard with it before you’re ready.
8) Not for shoulder per-se, but what really strengthened my neck muscles over the years has been practicing headstand the way it’s taught in ashtanga vinyasa yoga. (Sirsasana -> urdhva dandasana -> sirsasana -> childs pose).
During quarantine I started supplementing my regular yoga asana practice with Dylan Werner’s True Strength series and I highly recommend it if people are wanting an incremental body weight training series. Lots of mobility work in there too.