https://www.youtube.com/watch?v=A-30jb_vJUM
Make clear that "The pepper is going to be our virus (or germs). Pepper is NOT virus or germs. The pepper is going to show us how germs get ON and how to get germs OFF."
Reinforce the concepts: Repeat a few days later. Then when it's time for your children to wash their hands you can say, "Remember the pepper germs?"
:-)
For very, very, young children. Reduce the language and emphasize the action itself.