Just wipe it down with your shirt for a quick clean or use a microfiber for a better clean. Anything inside needs a clean and it's going to apple anyhow.
Thing is it's made out of sapphire so you don't have to be critical about what you wipe it off with. Shirt, cloth, etc. biggest thing is obviously don't saturate it in fluids.
I'm using Q-Tips now after wiping with microfiber to remove those small particles and it seem to work. I don't know if it can also scratch the glass like what tissues did