For various reasons I haven't been here for a while so just had to catch up on what others have said.
A couple of weeks ago I finally got round to trying out my new foamy bits because the weather was right: dry and not too much hot sun. I have to say that I wasn't all that impressed. It could be that I wasn't doing it right, or it could be that the Karcher snow foam jollop isn't much kop, or it could be that the car wasn't all that dirty so not much carp to shift.
Problem 1) was that I'd read a bit about this foam game and saw varying ideas on how much to dilute the supplied foamer before putting it into the bottle. Then reading the instructions on the Karcher stuff, it said nothing about diluting it. Thinking that this would be an expensive game if I didn't dilute, I opted for about 20% solution with 80% water.
Problem 2) was that the Karcher instructions said to use on a low pressure. But the pressure adjustment on my Karcher 7 is on the extended lance, which can't be used with the snow foam bottle.
Problem 3) was that the bottle didn't have any instructions about setting the control (?) knob. Trying it out adjusted the spray width a bit and seemed to alter the pressure from "jeez, that comes out quick" to "f***, that's powerful". Quarter of the bottle down, I set about directing it at the car, actually managing to cover everything.
Problem 4): after leaving it for 5 minutes to do its stuff I hosed it off with the lowest setting on the Karcher - and didn't think it was any better than if I'd just used the jet wash on its own.
The rest of the cleaning process was as normal. I just seemed to have wasted a few pounds, fortunately not that much, and 15 minutes. I'll just have to try again when the car has some real winter dirt on it.
(Not snow foam related, but I also did a little test on surface treatment. I gave half the bonnet some extra tlc with a pre-wax cleaner followed by polish then finished with wax. I honestly couldn't see the difference, whether in bright sun or shade. The only difference was the more glass-like feel of the treated side. When it rained the next day, the beading was slightly different on either side, but I wouldn't like to say that one was "better" than the other. I'm thinking that my once a year paintwork regime is more than enough.)