When my chin had problems figuring out how to use a Flying Saucer, I just put her on the wheel ( you should hold the wheel to make sure your chin does not fall otherwise they become afraid of it) and let your chin try to walk a little while you hold it, and he will realize how to use it! If he is already afraid of the wheel try giving some treats( like oats or alfalfa hay) to keep him on the wheel.
You can even get a toy like a small puppy or something and show your chins how to run on it!
Do not sell it, I'm sure they will figure it out, it may take time.