Just a quick one to say I use rainwater collected from a water butt as my shampoo water and also to rinse off using a watering can with no nozzle attached, since theres no lime in rain water it leaves a streak free finish and makes drying a lot easier Rain Butts are a definate investment for saving water and using as a great rinsing aid.
Always try and flood the paintwork also when rinsing, drys much much better.