NMF washing

I think this has come up recently already so I apologize for asking again.

Up until now, I’ve never even bothered doing a wash on NMF aircraft. However, this aircraft is a C-47 in the Zaire Air Force and I want it to appear fairly grimy. Doing a black wash on NMF just doesn’t seem right though. I’m thinking some kind of grey wash. What do you guys think?

Thanks.

A dark grey is suitable. I use Paynes Grey artist water colors or oils which is a little darker than RLM 66.

Regards, Rick