Tide marks

Jason the dark brown marks are the dark pigment I mixed into Gulf sand to darken it up. Its separated and made the lines.I can deal with that. The light ones, I'm trying to do to the effect that you sometimes see when dust adders to the brown and green but not the black of the camo paint (check picture) I've seen it on Abrams as well. I used lighter fluid as a fixer, it dries quick.
When you say not too much do you mean I should put more on. I do plan to lay down lighter color layers.