I have a 3G 20g iPod. If I wanted to add a shuffle to my arsenal, how would I do so? When I go to plug it in (either directly into USB port or via dock), how does it know which 512mb or 1Gb worth of music from my 15 Gb in iTunes library I want on the shuffle? I read about the AutoFill, but if I want to choose, do I create a Playlist called "shuffle" or something similar? Any help would be appreciated.