Using the snow foam about doubles the effort and time to clean your car. It goes like this.
Connect power washer to electrics.
Connect power washer to water supply (hose).
Set up power washer on one side of the car.
Pre-jet it to remove the worst of the grime.
Set up power washer on other side of the car.
Pre-jet it to remove the worst of the grime.
Snow foam it
Set up power washer on other side of the car.
Snow foam it.
Leave for 20 minutes to soak in and drag off another layer of grime
Look at ground and see snow foam collecting, with dirt dis-colouration to justify the effort you are putting in.
Connect up normal lance
Jet off snow foam
Get out bucket and sponge*
Wash down car
Jet off
Remember the wheels.
Takes a while and is definitely not for every wash.
PROS
Car looks great covered in snow foam, you are a pro now, congratulations.
Reduces swirls
CONS
You just wasted** an afternoon
If the power cable and the hose get tangled up, it's a bitch.
Care required to keep the power wash nozzle at least 300mm from paintwork, I like to play safe and keep it at least 0.5 metre away. Take care around seals.
* You're not really using a sponge I hope.
** depending on your outlook
I posted some photos of my first snow foam attempt, at
http://www.mbclub.co.uk/forums/detailing/144133-snow-foam-action-%5Bphotos%5D.html#post1630213