To represent soot and other associated grime that falls on horizontal surfaces, I have used Mig Productions Black Smoke pigment, applied with a filbert brush, where appropriate. This means cab roof, top of boiler, running plate, tool boxes, etc. The previous layer of Black Night PLW has helped this pigment to 'stick' to these surfaces.

I have also applied a small amount of Black Night to enhance the dirt buildup on the buffer beams.