Here is how I clean my car at the self-service car wash (my standards for car washing is not that high):
1. Drive into the car wash bay and park well in the middle. Make sure your doors and windows are shut!
2. Exchange for quarters so you can pay! (sometimes credit cards are accepted as well)
3. Pay for the time you need. In some self-service car washes, there is a minimum time requirement.
4. Choose the right functions (pre-soak, high pressure soap, high pressure rinse, etc.) to clean your car.
5. Start cleaning! Insert more quarters to extend the time, and switch between functions as necessary.
6. Keep cleaning until you’re done. Make sure to get all the dirty spots!
7. Use the foam brush if needed!
8. Drive away and hope the car stays clean :D
The overall time it takes to perform a basic car wash as such would be ~5 minutes (if all goes well).