HOW: Begin with the non-affected arm on an elevated surface. While hinging over at your hips dangle the affected arm. You will move your arm from front to back in this position initiating the motion from your body. If this is irritating your shoulder you can stand upright, the less you hinge over the less stress on your shoulder.
FEEL: You will feel the muscles in your should and shoulder blade work with this exercise.
COMPENSATION: Avoid overstressing the affected arm. The muscles in the affected arm should very lightly be activated, use the momentum from your body to create a majority of the movement.