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.
It should feel like holding a plank. When you’re climbing, especially on anything overhung, you’re trying to roll your pelvis toward the wall with your gluts and abs tensed. Your shoulders should be rolled back and down squeezing your scapulas together. Imagine a string tied to your pubic bone and sternum pulling you into the wall. Basically just have healthy posture to protect your joints and develop muscles correctly same as weight lifting. It’s especially important for a new climber who already has upper body strength. Source: I started climbing at 18 already doing 3 sets of 25 pull-ups and benching 280. I progressed way too fast with poor technique and tore my labrum and ruptured a bicep tendon. Good form, rest often, don’t grade chase or take risks.
Check out these books if you’re serious. I wish every gym had a short do’s and don’ts for safe technique with their orientations, but I’ve never seen it. This or anybody just telling me to slow down would’ve saved me a lot of pain.