There are a metric shit ton of muscles controlling your hand..
Sounds like you'd probably benefit from working on most of them.
One of the best ones in my opinion are farmers walks. Pick up something really heavy with each hand and walk for as long as you can. Do that a few times.
For pinch strength, I grab hex dumbells by the ends and walk around and hold them as long as I can.
Then there's the usual wrist curls (palm-up/palm-down).
Have a big bag of rice? Stick your hand in there and go from fingers fully extended to a fist a bunch of times. Work your way up to ball bearings, at which point you'll be able to crush animal skulls.