You can use a color adjust, bias and gain shaders to influence the greyscale masks you import, warp them, etc. For each use you could use another 'influencer'. Like now I'm doing a scene where I need small paths between grass, so I make a softish greyscale map, use one version for the texturing/displacement, and an adjusted version for pops of grass, and a third adjusted version for world opacity (to get the last grasses off the path).