Did I read this correctly that the music may be downloaded to a desktop & then distributed to the iPod?
Or are you going directly to the iPod on download?
Fwiw: "Manually Manage" - from the desktop computer is the only way I’d roll, if that is an option. May be pertinent to the original question too. Helps to bundle music in playlists. Then it comes down to checking playlists you want included, without weighing every song one-at-a-time.
Best bet too, I think (unless someone has a better idea) is to create an overview playlist of all music loaded that did not come from iTunes purchases (in case there are any of those in the mix). Sort of “maintenance” playlists to work in the background.
Detail:
I have a very large music collection, split between iTunes purchases & imported off my disks.
Not everything on my desktop needs to be on every device, especially if the iPod or iPad has a small capacity.
iTunes is turning into more of a sales kiosk these days (imo) & doesn’t play so well with music not served from their store. It breaks out PURCHASED items by default, not the inverse.
If I have temporary music snippets / guitar phrases I want to loop while learning them - those are useless on the other devices as music & I would not include them, or create an exclusionary playlist.
If I ran down the wrong trail, my apologies.