Hey Tangento, because of body oil and the normal abrasion of handling, the flat finish probaly won't stay perfectly flat very long, you'll pick up some shiny spots over time especially if it's any kind of laquer product, the best bet for cleaning would be to wipe it down with a soft clean cloth after playing, about once a week take a cloth, fold it up, and breath into the cloth, letting the cloth absorb the moisture in your breath, and clean a small area, keep repeating the process until finished. You are in kind of a Catch 22, the more you rub on this guitar, the more it's going to take on a sheen, the only other thing I would recommend is the occasional ( 2Xayear ) wipe down with a small amount of Naptha on a cloth, Naptha is the same as cigarette lighter fluid, just be careful, don't burn down the house, Have you contacted Epiphone? They should know better than any, I'd be interested in what they suggest.......
