This is the first time I tried to weather anything... and I over did it I think... What I did was dab my brush to grab a bit of of Trueline Warm Black, and then drenched the brush in dirty, dirty thinner. But before brushing it off on a towel or my painting board... I started to work it onto the RDC pulling as much of the black through the loco as I could. The places I really over did it are on the sides near the ends of the loco, and on the exhaust fans on the top (which are pretty caked with black thinner) I'm overly not happy with my first attempt, but think it could easily become one of my fav parts of the hobby... In fact I think locomotive modification is easily becoming my fav already, I haven't though about laying track in weeks since I started on my kitbashes!