Must say Chris for the first time ever I agree with Ian! IMHO He's no politician but he really does know what he's talking about when it comes to cleaning cars.
Two bucket method, quality polish if needed and then a few layers of wax or sealant
Lots of the rich/stupid Doctors at work get regular waterless valets and within a couple of years their paint looks dull and lifeless. My older cars gleam in comparison and theirs are almost brand new
Cant say Ive ever noticed it causing any scratches but it definately leaves swirls and doesnt give a perfect finish.
Then again i know im one of the few saddo's that actually enjoy spending a whole day cleaning my car