Start
Exercise 1. with 2 to each other throwing the ball, after first attacking towards the net, alternating.
Exercise 2. in pairs: run up with 1 ball in your hand and release it at the backswing (look where the ball lands!), alternating turns.
Exercise 3. each to himself: run with arm swing and other arm touching upper side of net (edge) [to get 2 arms in the air]. Throw the ball down (if that doesn't work, you can also ask to pass the ball in the air from one hand to your hitting hand).
Exercise 4
Pay attention to the run, not to the beautiful ball.