First: When you ready to clean them up, you should take rubber gloves first, it can do a great protection.
Second: For the big or very visible dirt & dust, we can remove them first. You can use large brush or shovel.
Third: We can clean with high pressure water gun, together detergent, like soap, laundry detergent
Forth: We need to sanitize it, this is very important, It can greatly eliminate the spread of the virus.
The last: Put it in a ventilated place to dry & reuse it again.