I know you're supposed to focus on the bodywork, but what kind of technique do I use to "separate the racquet from the hand"? Right now, my arm and racquet both move forward together and I just can't tolerate this. Obviously I want that 90 degree racquet lag to happen. For correct technique, it lags behind like there is a hinge between the end of the racquet handle and the hand.
Here is my video: https://www.dropbox.com/s/w3o6pupt6eoewjx/tennis.mpeg?dl=0
I would recommend opening the video in VLC and using the (E) key to go frame by frame for better analysis.