Washing mice and rodents can be very unhealthy. You could drown them or they could catch a cold. What you can do is give him some sand to roll in. You can buy chinchilla dust at the store. However, it is expensive. If you can find good, clean sand, then great!!! Your mouse may not like a sandbath. In that case, I can't help you.

Yes if the sand is on the clay it can roll even if the sand was not on the clay.The clay can still roll.

Alot of horses like to roll in sand or dirt to keep the flys off of them

They like themselfs to smell like sand and fish.

no