I've airbrushed the interior of the fuselage with German Dope Linen from Mister Kit Colors. I know that Eduard suggests to paint in Olive Drab but I think that dope is better because the green bands on the exterior of the fuselage were painted over dope...
Mister Kit Colors are, for what concerns WWI, very nice and on my humble opinion as correct as possible. But I don't like to use those paints; it's not evident. The best way to go with that I've found is to mix with Tamiya thinner... But even so doing, you must be very careful when airbrushing...