I once air brushed a Bell and Carlson stock and it came out better than the work they did. I used Rustoleum and mixed the colors to get leaf and twig colors. I cut stencils from cardboard consistant with cereal boxes and layered the leaves. I used a black base coat, gray twigs and browns and tans for the leaves. The leaf size was varied and the twigs were layered with the leaves for depth.I used black, white, brown and red for mixing and had a wide spectrum of colors. For air brushing I recomend one part paint to three parts thinner/acetone. The care you put into cutting the stencils and air brushing the leaf veins will make a lot of difference.
