I occasionally use the two bucket method. More times than not, I use one bucket. I usually wash at least two and sometimes four of our cars using the same original bucket and add a bit of water. I often leave the bucket full of the used wash water if I plan on washing the truck or some of the dirt bikes later. I do use a grit guard. Rarely do I see grit in the bottom of the bucket. I do see brown dirt deposits that coat the bucket bottom and sides (yes, I know that even fine dirt/grit can leave micro-scratches). Should I use a clean bucket for each car, in a perfect world, where water is not an issue and it is and always will be here in So Cal, yes. In practice, no need to waste water, or any other natural resource. Mind you, my vehicles just don't get that dirty out here near the coast. Wind don't get much dust blowing around. Most years we don't get much rain, and other than unfilled pot holes, we don't drive on dirt or gravel roads. That said, I can't stand a dirty car. Even a fine coating of dust bugs me. I wash our cars once a week, on occasion, more often. Haven't tried the waterless wash method yet. I suspect that the manufacturing of the waterless wash product, the shipping, packaging, etc. uses more water and gas than my 5 to 8 gallons of water used each week to wash my cars..............Keepin' it clean in San Diego. Phil