First buy a 30KG rubber grip ring, hold it 100 times at a time, and make several groups a day, which is very fast. (I gave the method of soaking worms, and I changed the latter two myself. )

The second is to buy a 40KG rubber grip ring, and hold 10 or 12 at a time (this may depend on your own strength, the weak one will do a few less at a time, and the strong one will do more at a time, but it is not recommended to do too much at a time). Both kinds of speeds should be fast, and several groups should be done a day.

Third, still use a 40KG grip ring, try to hold it for a period of time (time depends on personal strength), then release it, and so on. After practicing this method, I feel that my hand muscles are relaxed.

Note: it is not safe to throw dumbbells. Slide the dumbbell from your palm to your fingertips. When you reach your fingertips, throw it up gently with the elasticity of your fingertips. Catch, repeat.