exhaust smudges

[Lizard Racing]

Any tips on applying exhaust smudges to bodywork?

I have not found a thread to match this.

[Kit Basher]

I've done it on aircraft using artist's charcoal. If you want it really black, just rub the charcoal on it. If you want to do shading, rub the charcoal on some sandpaper, and apply the dust with a brush.