I hear what Robbie is saying, but I don't 100% agree.
For a car that is waxed, using a good quality car shampoo will act as a lubricant and the dirt floats off.
I prefer zymol sponges(as used by Paul Dalton) and 2 two bucket wash.
As a matter of course, since we don't have a hose, a few buckets of RO water( I have a large mega filter) will help to start.
2007 Audi RS4 Avant