Probably need abit more information to give the correct answer or ideas. To get your thoughts rolling, did your car wash provide a valet service or did individuals wash their own car?

If you can provide the necessary social distancing, you are servicing local cars, i.e within I believe its stated 30mins and payments are contactless, you have a good starting point.

You need to break-down each step of your service offer and examine, is it sustainable to maintain distancing and are my staff correctly protected.