I gave this idea a shot, worked out well. But just make sure you mix everything really good. I put a little dirt brown in and it was way to thick and I didnt mix it up all that well. So now I have little brown spots all over that you can hardly see but it gives the weathered affect. I dont know about the washing part yet. But thanks for the idea!
I tried this today. Looks great. But my question is now, eventually I would like to wash it to get the blah out of it. Is there a way to keep the color from leaving or will this have to be done again after every wash?
I just desided to burn some wooden matches and crushed up the burnt wood into ashes. then I just spread the soot on my fingers and smuged the soot into the weathered areas. looks good but needs the sand color