Oh ma' Gosh . . . Brian. . . Testors Dullcote is Laquer!!!!
So you need laquer to thinner Testors Dullcote and also
the same Laquer thinner to clean out your airbrush.
Warning, Laquer thinner is harmful if breathed into your
lungs. So make sure you have a window open, or your exhaust
fan going. Or a mask over your nose and mouth. Yes, I really
like Testors Dullcote for giving a very nice even dull finish
to a model or figure. It is the best product for this kind of
issue, that I've ever used. But you do need to be careful. It is
LAQUER. . . so be sure to be careful and thin it with Laquer
thinner. Wishing you well. . . . The Miami Jayhawker