This exercise can be done with your arm resting on a table or your thigh. This allows the movement to come from your wrist and working your forearm instead of compensating with your shoulder. Start with your hand in a position that your pinky is resting on your thigh or table. You are going to allow your wrist to rotate both directions in a controlled way. Full range of motion is palm facing down, and rotating the other way so you end palm up. Your pinky is resting on the surface the whole time. Try to hold the end of a Dumbbell to create an opportunity for a longer lever which takes more effort to control.