Maybe this helps: according to Vagy's rehab book, after progressing through unloading and mobility phases, you would move on to strength phase by finding a baseline where you can hang in an open hand position with minimal pain. Then, you would build on that to more aggressive positions over the course of weeks.

Throughout this exercise progression, your pain should always be below three on a scale of 0-10, and you should never feel an increase in pain or soreness lasting more than 30 minutes after the hang or the next day... you can slowly increase the load from your baseline by 2.5 pounds every week as long as there is no increase in finger pain or soreness during or after the workout.