Watercolors, huh? interesting.I guess when you have the thick watercolor straight out the bottle it can get pretty dark. I loveeee rusty cars like no one else. Yours looks cool, I just think it's got too much black. Remove some of that dark black and let some of the natural car shine through. At least so some of that UP logo and that "we can handle it" logo shines through, You don't wanna block that out completely. I'm no expert by any means, my weathering sucks, but that's my humble opinion anyway. You're probably better than me. But remove some of that darkness, and see how it turns out. I'd be interested in seeing the changes.