I keep a small tupperware-type plastic container filled with water on my work bench, and, between colors, I wash my airbrush out in it. It doesn't matter when the water gets a little dirty. Last thing I do between coats is fill the cup a little with airbrush cleaner, and back flush, loosen the needle and work it back and forth, and then spray out the remainder of the clean. I make sure I've worked the needle thoroughly, and then I move to the next color. When I'm done spraying, I do the same thing, making sure to clean the tip with an artist's brush (throw away), and then I run cleaner through it one more time, and then hang it up until the next time I paint. I pull the needle out before I paint again, and, if it's still dirty, I clean it and run a little acetone through the gun, and I'm ready to go again. Most of the time I don't need the acetone. And the "dirty" washout water works fine. No running to the sink. The airbrush cleaner last step takes care of any residual paint from the "dirty" water.