Each to their own as far as use and method concerned.
A lot of caravan sites have a no car washing policy and I can understand that because of water waste and nuicense.
Our site has quite a contradictive policy though. No washing of car or caravan, but you must have your static van cleaned annually using their approved contractor, also if a car or caravan is too dirty on arrival at reception the owner is asked to take it away and clean it.
As I said earlier, I bought a pack of showroom shine as seen on tv. I tried it out yesterday on the nearside of the caravan where we have a couple of spider camps. As you might know, spider deposits stick like the preverbial. But after a 60 Sec soak all was easily removed.
The product I have says it has a diluted petrolium distilate and canuba wax as it's main ingredients.
My Abbey has GRP side panels which seem ok with the cleaner. The only painted panel is the aluminium roof, which I'll tryout the cleaner on soon. If it removes the green grime off there, I'll be chuffed.
I do agree that if you don't remove the loose deposits of soil etc with a watering can of water first, then there could be potential for scratching to occurr. But taking into acount the pros and cons it seems a good product for light cleaning to remove say a long drive to the destination.
Technically it is a waterless cleaner so as such, you could be deemed to NOT be washing your car or caravan.