It's funny that the author didn't think to try Music.app instead of doinking about in Finder. I just did this a couple of weeks ago with my own iPod Classic: Music supports iPod sync just fine. (Yes, still!)
they work great with Clementine, too, which is cross-platform. and with a SD/flash adapter and Rockbox, the older models can still be capable little devices today. rockbox, at least, does start to chug a little with dynamic playlists over several thousand songs, though...