Every few months I will self wash and put on a really good wax. After that I will go to the coin-op and do the following:
1. Hot soap wash. I don't use the brush, I just spray.
2. Hot rinse or wax.
3. Spot-free rinse.
I then hop on the highway for a few exits and turn around. Very few spots if you get full coverage on the spot-free and all the dirt is gone. The key here is to have a good wax application and the car will clean up really nice without touching it.