Thought I'd try this as I don't have a pressure washer and didn't cost much.

It foamed up really well but ran off the car very quickly. I think if I had a pressure washer to then rinse it off the car would of came up better as I had to use a wash mitt which defeats the whole object of the exercise and as I'd have to use a pressure washer anyway I'd might as well have a snow foam gun.

End verdict is waiste of time and money but thought I'd try it.