Have you ever known a technique, then forgotten it completely? A couple of years ago, I learned a technique where I could take a texture, lets say it was metal, then using another copy of the same texture, perhaps desaturating it, I could use it to make the original texture look as though it had the 3D bumps and cracks that would appear in the real world.
I haven't used this technique for a couple years and now I can't for the life of me remember how I did it. I do remember it being really simple. I have tried displacement mapping and CC Glass.
In my memory it seemed I learned it From either AK or AR, but I have searched every tut they have done. I have tried everything I can think of??? When I finally remember it, it will probably be so simple I will have a V-8 moment.
Stylize > Texturize is what you need.
Rather than desaturate the duplicate layer, I'd suggest using Set Channels, and change all the channels to whichever one has the highest contrast.
Then apply levels, and increase the contrast more.
Now use this layer as as the texturize map.