The best coin op wash bays I've seen is at Fifteenth street in mildura with six detailing bays. I don't touch the brushes either. Only use them as a high pressure rinse and spot free rinse on my car to keep it as best I can while interstate.
It has the best high pressure guns I have ever seen

99% of time I do it at home where I can do it safely using my 5,000 litre rainwater tank instead of mains water which is $$$$$ these days