Originally Posted by Ender Hey Steve. The type of structure may determine the best phasing for painting and installation. For lasercut buildings I usually paint the exterior and interior on the uncut sheets, the interior can just be spray paint black or brown. For plastic/styrene buildings, I usually assemble the walls and either roof or floor, so everything is fairly stable. Then spray the interior, then the exterior. Or sometimes I get too excited and paint the exterior color first, then I ...