Cleaning the Nexus 6 topic

Hey guys and gals, I've got a midnight blue nexus 6 and I've noticed that the back of it is really bad for holding oily residue and finger prints. Does anyone know what we can use to clean it?? I want to keep my device as good as new, I was thinking about getting a clear skin BUT I wasn't sure if the adhesive could ruin the back!? HELP!