I'm attempting to do this without having to create  additional texture maps.
The end result is that I want to create a texture where a person can input their two texture maps (base texture, then texture with clothing on it (second skin)) and have instant displacement. Much like Silverblade's Dirt mat where one only has to input the texture they want to 'dirty'.
I think I'm on the right track using a distribution map, but can't get true black and white values from the end result of subtracting the two textures. Gray scale is all. And the slightest amount of gray in the distribution gives some pretty wild results...

...Insert some witty or thought provoking comment here...