well everything turned out great. I used a mix of 10-3-1 of water-
grimy black/ black- and dish soap. I let it stand just until it looked like
the surface was drying through (a few minutes) then wiped away with a
damp (not wet or soggy) towel. I used this on my Mig 21 and a 1/72 163 Komet. I'm very happy with the result, it added quite a bit of realism. Thanks everyone for the input.