I was worried about this exercise due to my history of left shoulder instability, but it seemed like the best progression toward a back lever (and probably a front lever too), so I wanted to try it out.
I started with the rings at chest height and walking through them. This allowed me to stretch my shoulders into the bottom position while my feet were solidly supporting my weight on the ground.
To my surprise, my shoulders fared just fine.
I played around with it until I felt comfortable with my full weight hanging in the bottom position, and then I .
It was rough in the beginning. Most of the tutorials I watched were just explainers. And the ones that did offer instruction mostly focused on the second half of the movement.
I would lift my knees up, and then go nowhere? I thought I just needed to be better at hanging leg raises. But after more playing around with it, I realized it was the lats and scapula doing the heavy lifting.
I spent a lot of time with the chest-high rings, kicking up, trying to control the negatives, and really just playing around until my grip gave out.
I finally found a progression video I liked: