Basecoating with vallejo air

[Jasio]

I want to basecoat my army with the vallejo black brown. Is it a good idea to airbrush the colour (model air) directly on the plastic/metal or should i use black /white primer first ?

 

[ScottRadom]

You want to use a primer first. A primer puts down a surface that bonds, kind of "bites" into the surface. This differs from regular paint that doesn't attach to the surface with the same tenacity. Painting directly onto the mini's will mean that as you game with your mini's even if you seal them the pant will rub off FAR more easily.