How do you guys clean your device's screen? Usually, a fingerprinty screen would not bother me, but it's getting kind of bad. The oils from my fingers, I'm guessing, are starting to dry, making my screen have a rough surface. Also, today, someone was opening a carton of chocolate milk near me, and a drop flew off the cap, onto my iPod touch's screen (what luck). Now it is really dirty, the chocolate milk dried, and there is a noticeable patch of roughness from it. What is the best way to clean it? I heard that glass cleaner is a big NO.