Im trying to make an aged surface.the first texture is a metal surface and the second is something like dirt,for both i made the right bump maps and a alpha map for the dirty map.what do i have to do to see the dirt on the metal surface,i tested some functions but nothing really worked for me,sometimes i only see the metal surface and sometimes only the dirt or some big white pixelpoints on the surfaces.What settings should i use to mix them correct???