If you have water restrictions, you may want to consider doing a rinseless wash with a product like Optimum No Rinse. DJ Mayo has put together a great tutorial on how to use this product without having to use a hose or a lot of water. With a black car, it will get dusty from day to day, and your best option is to simply allow it to get a bit dirty between washes. If you attempt frequent “wipedowns” to get rid of the dust, you significantly increase your risk of adding swirls. You could use Optimum No Rinse in a spray bottle, thoroughly spray down a panel, carefully wipe it down with your microfiber towel (that has been made wet from the ONR spray solution), and then immediately dry it off. Then move on to the next section. I would only use this modified Optimum No Rinse procedure on occasions when you have very light dust to remove.