I love these threads. After 8 years on the road (and a gravel driveway) mine is well-worn and is lucky to get a really good washing twice a year. What it usually gets is the coin-op. Spray, then fill a bucket and scrub, then rinse, then wipe off whatever snuck over the edge onto the seats.
A couple weeks back I spotted a carwash fundraiser run by my old HS football team so I swung in and let them do it while regaling them with gridiron tales of daring-do from the days of yore.
They were very careful and did a decent job.