Carry enough water to ONR wash, use customer's electrical hook-up, been doing it that way almost 19 years, no one has had a problem with me plugging in. I shampoo carpets and wetvac, although I am looking into a steam cleaner to see if that speeds things up. Have it to such a science now though, not sure if changing things up will speed me up or slow me down.
Everything right now fits in my trunk, cooler and ladder (when doing trucks and SUVs) in the back seat, so no need to pull a trailer. Makes the AZ trips twice a year a lot cheaper on gas with everything fitting in my car.