gzhpcu
Professional
I used to have a problem getting the correct "windshield wiper" action on the topspin forehand, until I realized that what helps me is when I am at the bottom of the forehand loop, coming forward with my wrist laid back is to supinate my forearm. This ensures that the racket head is really down low and gives a maximum pronation range of the forearm when hitting the ball and continuing with the follow through.