DO NOT ADD TAMIYA THINNER TO VALLEJO PAINT

I can not stress this enough, that is unless you like cleaning a gooey mess out of your airbrush.

Tamiya and Vallejo are both acrylics, but are not the same type of acrylic. Tamiya acrylic thinner will actually gel Vallejo paint.

DK....how much are you thinning it? Just sounds like it isn't thinned out quite enough.