I am planning on doing a light wash with combo of black and earth colored abteilung oils on a grey with light blue underside La-7, then near the end of build apply some MIG dust colored pigments right out of the jar with no thinner, add a little dried mud to wheels and underside.....sound like a good idea? little confused about what airplane scum looks like.It must be variable....I assume and most I have seen is a combo of brown black scum with oil stains in the right areas?

Hi doppleganger
If you are looking for some subtle weathering of your Lavochkin La-7 have a look at Robert Willis's work https://aeroscale.kitmaker.net/forums/156947&page=1 . Or Kamil's heavily weathered Yak-9t https://aeroscale.kitmaker.net/forums/156730&page=1
All the best
tim

no pics on the 2nd link? I just see boxes with red x