a) How do you guys clean the ipad screen? Just a damp paper towel, or something fancier? b) User guide says to charge the battery to 100% and then take it down to 0% once a month. Does this mean no charging the battery during that time, or can you, for instance, let it get down to 25%, then charge it back to 50%, then take it down to 0? I know plugging it into the PC's USB port causes it to charge a little (despite what the display says), so I just want to be sure I can do this during that time.