painting scenery

so I just finished making this really great building, I've sprayed a basecoat on it, and have begun to paint it.

I used spackle to make a stucco effect and have begun to paint it an ivory color for an undercoat.

Here's where the problem begins, the paint i got, some cheap stuff from AC moore, is really thin and i realized i might need to use at least three coats of paint to even get close to the effect i want.

Is there any faster way to do this?

I was thinking of using the GW spray gun but aren't sure if i should put that AC Moore paint through it.

Any suggestions?

yeah, do not basecoat it? - or a basecoat close to your intended colour... that way you won't really notice if the paint doesnt fully cover...