My local garage (and im sure many more) charge you for x amount of minutes and in those minutes you can select a variety of different things, like high power jet wash, hot foam, hot wax, 'long reach broom', hot shampoo etc etc.
I am yet to buy a pressure washer and a foam lance so have never snow foamed my car but what do you lot think you heading down there, giving it a spray off and then getting loads of the shampoo all over it? Just like snowfoam. I wouldn't be using any of the there cleaning tools just the pressure washer and the shampoo that sprays out? I'v also got some wolfs brake duster that I could leave to dwell and then rinse of while I'm there...what ya reckon?