$30 a gallon isn't bad at all. I think a gallon of Zaino would run you more than that. I'll have to try the ICE when I run out of Zaino wash. I was told by a detailing expert (owned his own detailing business and I saw his work) whatever you do use soapy water. the suds lift the dirt and particles off the car so you cut down on swirl marks. I was washing my first black PT with water every week, no soap. Apparently that wasn't a good thing to do and it did have swirl marks.
One other suggestion for you...make sure you wash your wheel wells. They "frame" your tires and wheels and nothing looks worse than dirty wheel wells when the rest of the car is clean and shiny.
One of my ****, pet peeves.
Good luck with your car washing.

Pat