I like to keep things as simple as possible. For whatever it's worth, IMO if you want to hit something a pro like fh, with all the spin and racquet whip that entails, then:
- Get into a decent load position (left arm across the body, some bend in the legs, open to neutral stance with the back leg behind the ball)
- Swing the edge of the racquet across the path of the ball. The swing path follows the edge. Generally your racquet face will be somewhat closed. How closed depends on a bunch of stuff - you'll figure it out.
Obviously there's a lot more stuff that can be said, but if you do those two things you will get a ton of spin and the shot should feel pretty good. It will feel way different than hitting through the ball flat. You'll also shank a lot of balls at first. You even don't need to swing fast - just edge of the racquet across the ball's path. It's a lot easier if you keep the rest of your body as quiet as possible near contact.