We've tried out a lot of good quality waterless wash products, such as Optimum No Rinse for example, which gets rave reviews in the states, but we've yet to be able to use any without causing marring, no matter how carefully the paint is wiped down. Our view is that you need water to be able to wash a car safely in the UK, mainly due to the grotty state of our roads. How about getting a portable 12V power washer with onboard water tank instead? Okay, so they are only good for shows, but still a lot better than a wipedown with a waterless wash product...