My dealership uses a guy with a power hose who seems to do a pretty good job in fact - I don't mind them doing that but the day they install something with anything that whirls at high speed and hits my paintwork is the day they dont wash it anymore... Yes a nice soft chamois is fine when you are gently wiping off water with it - spin a chammy at high speed, dont rise the grime off it and its the equivalent of beating the truck's paint with a stick.