Place a swiss ball on the wall and you palm on the bal so when its in the middle of the ball, your hand is roughly at shoudler height. Lean some body weight into the ball, keeping yuor arm straight but rptracted / pressed away from the ball. Slowly roll the ball in a anti-clockwise circle as big as you can with losing control. Don't let your elbow bend. Repeat 10 x and then go 10 x clockwise.