How do you teach top spin?

TECHNIQUES FOR FOREHAND AND BACKHAND

For better understanding of top spin, let’s imagine that instead of tennis ball,
an apple is coming to you. Instead of racket you have knife with the razor up.
Now, peel the skin from from down going up.
Depending of the type of spin, you can cut thin or thick.
Thin cut means more spin i.e. more rotation but more slow ball.

There is another move used in spin/ top spin. That is when you “cover” the
top of the ball.

Let’s imagine other picture.
Imagine that the ball coming is huge ball, 1m diameter, with face and hair combed back.
Now, make the motion the same as with the knife and apple but you have a comb
in your hand. Stroke, with the comb, under the chin, over the nose, forehead,
top of the head and just continue combing the back of the head a bit as well.
This type of top spin is better quality stroke.

What is the wrist doing exactly in top spin?

Wrist in Forehand behaves the same as left wrist in Two Handed backhand.
When the wrist is bent backwards (dorsal flexion), it has two end positions.
If we talk about Forehand, stretch your arm forward, half right, where the contact
point should be. Imagine that your palm is on the clock. Your fingers should be
pointing at 4 o’clock while the wrist is in the lowest position and in the top
position you fingers should at about 1 o’clock.
This is what gives the spin beside the arm (from the shoulder)movement from
down up.