you need a lance for it but as mickie has said its supposed to be good stuff.
however most snow foams are more a traffic film remover - snow foam was designed for washing wagons and aids the cleaning by sticking to the paint long enough for you to wash it off - rather than an actual shampoo so can strip off waxes, sealants
as for does it make a difference not really. it more for non contact cleaning.
hose the car down with low pressure
snow foam - its supposed to lift the dirt off the paint work
rinse off
means your not rubbing the dirt off or scratching it off with the pressure washer