Many of my cars come from the collections of modelers who have died, so I try to keep their work alive by doing little more than changing the wheels and couplers. In the tanker's case, the original owner fudged the decaling a bit. I made it appear as though it was burnt in that spot like so, using rust then flat black. I finish by painting the wheels Testor's Rust and the trucks with Testor's Rubber paint. I do not clean the brush as I alternate between the two colors.