On weekends and whenever I'm at my wash I spray tires before customers enter my automatic bay. I use a tire cleaner that isn't corrosive, is safe on paint and works good on bugs and road grime. I got tired of mixing up the chemical, pumping it into a 2 gallon garden sprayer and spraying it on cars. So, I made a delivery system out of two five gallon chemical jugs, a hydrominder, a
flojet pump, two air regulators and a home made foamer. I put a quick connect on the foamer and I mounted it on the wall outside of my auto bay. I have a 30 foot hose that I have a triple foam gun on and a ball valve prior to the gun to turn the chemical on/off. Easy to set up and easy to take down. Takes me about 30/45 seconds per car to spray tires, bugs and other bad spots. Customers appreciate it and I get a lot of positive comments about the added service. No question in my mind that it helps to keep customers coming back. I'll take and post some pictures of my setup.
I've thought about trying to get kids to work for tips after the auto wash. Hand drying, tire shine, vacuuming....whatever the customer wants. Maybe charge a small amount to cover the cost of materials. If the kids would hustle and do a good job I'd bet they could make some decent tips.