I'm not sure what you are eating for lunch but I remove most of the smudges and finger marks from matte black frames with a cloth dampened with LJ glass cleaner.
It's a very good habit to wash your hands every time you come back from lunch, scratch your head, pick your nose, or whatever and before you touch anything in the shop. I usually wash my hands about 5 or 6 times in a work day. Once you form the habit it isn't that time consuming and it will guarantee that someone else is putting all those finger marks on your frames.
You would be surprised at how much grease french fries will leave on your hands. And it transfers to the paper cup that your drink is in (yeah, the same one that you got a refill in and brought back to the frameshop) and hangs around all afternoon just reapplying itself to your hands every time you take a drink. I would shudder to think what that stuff will do to a Moorman suede or the cover paper on a rag mat in a few years. I can just imagine all those greasy finger marks showing up with age and getting darker and darker and ...............
Framerguy