I want to have the characters in my game, when they come out of the water, be able to be wet using a specular/reflective shader. I would like, the longer they are out of the water, the drier they get, and the less the specular wet shader affects them. Is there a way to control the amount that a shader is applied? I know how I would write the formula, but I'm not sure how to apply a shader less than 100%.

Also, is there a way I can use a greyscale skin to dictate the areas and amount of the application of the shader? (i.e. where the map was black the shader would not be applied, but where white all the way, and grey it would be applied at half strength.).

Thanks so much,
Stonerunner