Apply a secondary texture/material?

I have a model with a texture, I want two variants, one with grime, and one without, default is without. Is there a way I can have it so I can apply a transparent material ontop of the existing base material?

This is so I dont have to have 2 variants for 12-14 skins.

You can use $detail in your material, but I think you’ll still need those 2 .vmt variants per skin. You might get better help in the modeling section.

I’ve tried to do the same thing in the past (http://forum.facepunch.com/showthread.php?t=1566403) but I couldn’t really get anything working without weird hacky rendertargets.

I know that really isn’t much use for you, but I figured I’d let you know that I’m interested in doing the same if you figure it out.