I tried pencil too Wurger, but that didn't quite cut it for me, that's where the ModelMaster Metalizers came in (mostly the darker ones such burned metal and exhaust). I didn't apply them as usual with the airbrush, but rather dipped a cottonbud in the bottle and let that dry up for a bit (as the solvent is pretty aggressive and easily strips off underlying paint coats and such) and then kind of rubbed/dry-brushed the metal particles on the appropriate aera's such as edges, the profile on the tracks and such. Come to think of it, I could have tried graphite paper as well.