Kneel with one knee on the ground, other knee up in front of you. Raise a light Dumb bell up to a 90 degree angle out to the side. Very slowly bring the arm all the way in front of you and across you into an internal shoulder rotation then slowly release and take the arm back into an external rotation, then return to starting position and press overhead. Only go as far as your mobility will allow, while always trying to safely increase your personal mobility. The key to this exercise is to move very very slowly and thoughtfully through each phase.