Imagine a 65 year beginner that can't learn the trick for volleys. Do you make them do pushups when they fail. Not likely. 65 year olds couldn't get up off the ground without help after trying to do one pushup. I'd suggest using carrot cake rather than the stick approach. The cake is success without much pain and lots of encouragement.
I might show them racket drills for volley skills that they can practice at home. This allows them to improve their ability to control a ball in the air. I use this for kids and beginning adults. Dribble the ball on the court with the racket and then do the reverse just bouncing it in the air. They can learn to reverse the racket to each side, catch the ball with the racket l, and then graduate to moving short volley drills with a partner down the net.
Or, you can send them to a wall and have them keep the ball in the air against a wall. Go to 3:58 on this video and it's something to show your student that they can practice on their own. This is a good training video.
https://www.youtube.com/watch?v=GU7mq8uZgJo
