One key thing to keep in mind re: Internal Rotation is that after the ball leaves the hand at release (6 o'clock), where you finish with your arm and hand has ZERO effect on the pitch. That is why IMO the whole focus on IR should be what happens PRIOR TO release and just let the hand and arm finish naturally somewhere out in front of the body (e.g. arm goes up to the left shoulder; hand flops around like a butterfly, etc).
Getting the arm and hand in the "correct slot" from 12 o'clock to 6 o'clock is where the arm whip (IR) happens, generating all of the speed and spin on the ball. The FINISH is just the by-product of proper mechanics that are happening well upstream of the actual release of the ball.
Getting the arm and hand in the "correct slot" from 12 o'clock to 6 o'clock is where the arm whip (IR) happens, generating all of the speed and spin on the ball. The FINISH is just the by-product of proper mechanics that are happening well upstream of the actual release of the ball.