About a year ago I switched from hangs/lifts to curling with a force meter. That's nice since it makes it very easy to auto-regulate: I'll set force/rep, reps/set, and sets/workout cutoffs and just do as many reps per set and sets per workout as possible within those parameters. 80%/8/3 with two grips worked well for me for strength. I haven't trained endurance but I think this method could easily be adapted for that.
To illustrate with some easy numbers, if my max in a grip is 100lbs, then I'll…
- Perform as many reps in a set as possible, stopping when force drops below 80lbs or I hit eight reps.
- Repeat for three sets, resting fully between sets. (My three-set cutoff came about from experimenting with an auto-regulated set cutoff; three ensures I can train both grips effectively.)
- Move to the next grip (with a corresponding force cutoff).
A rep is just a 2–3 second maximum contraction with slow onset. I built a little platform out of scrap wood that I use for this, standing above it as if doing a mid-thigh pull. I try to curl solely with my hands and avoid shrugging the weight.
For grips, I do one where I pull with a flat fingertip (targeting the FDS muscle) and another where I try to curl the fingertip into the edge (targeting the weaker FDP muscle). If I want to target specific grips like small crimps or pockets, I no longer even try training those on a hang board. I just set specific problems on my woody targeting those grips and do lots of static-y sets on them.
FWIW I think you could adapt this methodology to a hang board, but you'll have to be careful / self-aware to match perceived effort to actual output. It's a lot easier to overdo the intensity and volume on a hang board than with a force meter, so erring on the side of "too little" is probably a good bet.