Disclaimer : it's all perfectly legal just so we are clear
There are some self-service car wash stations that seem to be really cheap - like "car wash for only 50c!"
You know you are going to spend more since two quarters only buy you like a minute 10 sec or something...
But you can still take advantage of the deal What I usually do - I turn it to brush with foam and put 50c or 75c in. Then you need to go around your car pretty fast for next minute just so you have foam on most of your car. What happens next - foam is no longer coming but you still have a brush in your hands! So use it for as long as you want (within reasons of course) - just go one more time around your car and see if you missed any spots - nobody is counting time now.
And when you ready - just put in 50c or 75c more and wash everything off with high-power rinse.
You are done! Now you can go to Starbucks and spend your well-saved couple bucks
Good idea for a 'beater' but I don't use a brush on my car. A brush will tend to put minute scratches in the finish that show up in reflections and eventually leave the finish 'hazy'. I'll give you an 'A' for ingenuity though!