How to make fingeprints /grease stains

[karaokefreak_1]

Hi
Simple question:
Using Unity 5, how do I make something like fingerprints and grease stains that make a glossy material appear used when hit by light?

To make clear what I am looking for: I don’t want to have contrasty dirt and scratches. I want the material to be less glossy at some places. Like when you use your cell phone a lot and don’t clean it. The screen won’t be so brilliant any more, but all smeary.
I need it for the surface of a musical keyboard, since it is way to clean. see screenshot.

Thanks for your time & support.

[karaokefreak_1]

Ok, the answer is: Specular Maps. Transparency in specular maps will cut out the gloss, dark colour is less metallic or less glossy, bright colours equals in more gloss or more metallic reflection.

[karaokefreak_1]

The result looks like this

[theANMATOR2b]

I’ve just recently learned - additionally - on standard shader (metallic workflow) this can be controlled in the metallic grey scale texture and painted into the albedo.