Back in the early 2000s, both Padraig Harrington and Vijay Singh would work on their body connectivity and rotation by using a glove under their lead arm. This would also keep their hands from getting too high in the backswing.
I prefer to put the glove under your trail shoulder, but the principles stay the same: keep your arms connected to your body and force yourself to learn to rotate your body through to keep your face square instead of trying to save your swing by flipping your hands.
