I've just found a very good way to exercise both hands .
There are theese metal or marble balls called sometimes chi-kung balls or on many other names.
Theese are two balls with a spring and another ball inside.
You have to rotate them constantly in your hands. Two balls in one hand , two balls in the other hand.
After a while your hands become extreme loose and rapid.
You have to start the exercise with the smallest balls possible. It is not easy to rotate them in the beginning, but after a week practising a few hours every day , you'll be a master of them. Then you can buy any size you can handle.
After a week exercising with the smallest ,i've bought the biggest one. They are very good to the hands, but they are also good for your health.
They used it a lot in the ancient China for preserving health , increasing energy ,or just for doing something.
They make a chill-out noise also like smooth bells. Try this out!