After dismantling the Class 14 diesel, I took the chassis down to the sptray booth and mixed up a nice paint cup full of Precision Dirty Black paint. For some reason the paint was the consistance of double cream and filled the jar to the brim. I've no complaints but is was a suprise and took more thinner than normal.
There are a lot of nooks and crannies to get the paint into. Using the airbrush was the right move as doing this by hand would take ages and more than one brush I suspect.