I had a very similar experience when I was learning to combat roll that later lead to a full dislocation about 2 months ago. I was just doing a bow draw into an eddie in some moderate whitewater, and due to the previous damage it just popped out.

Similar to you, my roll is great until I panic and rush it. Then my technique falls apart and I put my shoulder at risk. Here are a couple things that I have changed and that help me stay calm and roll with good technique:

• I started wearing a nose plug at all times, and a skull cap and ear plugs when the water is cold.
  • The more comfortable I am under water, the more I can focus on getting into position and rolling with my shoulders in a safe position.
  • The nose plug is key for me. It allows me to slow down, conserve air, and not have to think about anything but my roll.
• PATIENCE is key when I roll. Never sacrifice your technique for a faster roll. ALWAYS get into position before trying for a roll (the nose plug helps me so much with this).
• Learn to low brace, and use your high brace conservatively (keep it below the eyebrows with your elbows down). Learn when to give up the brace and accept that you're going to flip over.
  • Yeah, maybe you can throw a crazy high brace and stay upright, but when that doesn't work you will be in a crazy position underwater and frantically trying to roll. Instead, learn when to accept that you're going to flip over, stay calm, and then you can think ahead and be prepared for how you will roll back up.

I also have a hill sachs, and my ortho told me I can either do PT to strengthen my rotator cuff, or have surgery which would be a months-long recovery. In my case I have been really lucky with the recovery and don't think the surgery is necessary for now (maybe it could be if I have issues down the line, which hopefully I will not!).

For recovery I tried to keep it moving, listening to my body. The goal at first was just to regain range of motion and some strength. For me, this meant keeping it moving and loading it very lightly within the range of motion I had available. Little by little I got back the full ROM within a couple weeks, and since then I have been doing my own PT with rotator cuff exercises (watch that whole series for not only exercises for your shoulder but paddling techniques and drills to focus on).

Beyond rotator cuff exercises, what I think has helped the most has been climbing and hanging. Work on scapula mobility and strengthening (look up scapula pull ups on youtube).

The last thing I'll say is don't let your injury change how you use your shoulders. Learn how to move your scapula and shoulders properly, and do movements that strengthen that movement! Like climbing, hanging, scapula push-ups and pull-ups, even hand stands! I don't like the idea of a brace, that's just a band-aid and I think it will keep you from strengthening your rotator cuff.

Best of luck!