The pic below shows wrist strengthening and mobility exercises. The pics on the right show me progressively warming up my wrists and shoulders. The pic on the left is me going through the drill, which involved 30 second holds.
The pic on the left is another challenge which involved developing more knee control, while maintaining a tight verticle trunk. This involved 30 reps.
The pic on the right shows the development of single arm strength. Thing to remember is keeping tight the whole time, no saggy back, 50 reps!