Very simple exhuast stains...

I'm my never-ending quest for the quickest, easiest way to do anything, I've found a simple, quick, easy way to make exhaust stains on aircraft. You'll be suprised how simple it is-

Take a No. 2 pencil
Color in wherever you want the stain to be
Smear it with your finger to the proper "consistency".

The advantages of this method are the fact that it's cheaper than using pastels, and (I think) more control. That, and it's foolproof! I've had more trouble keeping enough on than putting on too much. The only problem with this is exactly that- getting enough on to look good. It might disappear on darker finishes, and even on lighter ones it takes a little to look convincing. But the effect is very subtle, and when that's what you need- it works!