for grip training.. I hang from a pull up bar, gets a few more body parts done at the same time.. finger tip push ups (against a wall, not mad enough to go to the floor yet) to help balance things out a bit, the bar for second, but every now and again every day, helps stretch vertebra and intercostal alike as well.. I'm not a fan of grippers, mines were pretty weak, but It felt like reps gave me more fatigue than hanging does, though it didn't help that I was a cable puller at the time lol

finger tip push ups are 2 sets low reps.. like 3-5 depending on how cold my hands are, but really slow trying to squeeze every bit of gain out of an easy exercise

a lot of arm swinging qi gong, Jam Jong with intention in the palms and fingers, which I've only recently got back into, so it's not long before fatigue sets in