There's a myth - mainly put about by the snow foam makers - that snow foam will give you a touchless wash. While they will pull some dirt off very muddy cars, they won't do much visibly to normal levels of dirt. What they do well though is to soften the dirt, so when you do drag that cloth across your paintwork a lot of the dirt is softened and encapsulated in the detergent. You'll get a similar effect by spraying the shampoo on the car, but it won't dwell as long as snow foam. Unless you've got a well polished car and are a bit obsessive, you'll not really notice the difference.
I should point out that there are some foams such as Bilt Hamber Autofoam that will take a layer of dirt off, it is quite alkaline at ph 13/14, so you need to get the dilution right if you're not to prematurely wear away any wax or sealant you have on the car.
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