...alternatively, grab your wifes best hand towels, lottsa McG's or Mothers in a bucket, cold car, rinse as much dirt as possible with a hose, then start on top, wash all horizontal surfaces, then top of sides to door bash rail, then lower panels, lastly around wheel arches. Rinse as you go, before water dries. Then when finished (this is the fun part), hose all over, then hit the road - motorway is good. Drive her til shes a dry. Last step, hand towels in the washing machine. Wife will never know.