Quickest way to sync new ipod with old one?

Hi all - I have not been able to find an answer to this specific circumstance, so I'm hoping someone here can help... Here it is:

I have two Nanos (we'll call them "new" and "old"). All of the music that is on the "old" Nano is on my MacBook, in iTunes. I'm not switching computers, fyi.

Because I have thousands more songs on my computer than are on the Nano, I would like an easy method for putting all of the songs that are on the "old" device onto the "new" device (easier than manually locating them in iTunes and adding them to "new" Nano).

The solution might have something to do with syncing, I dunno. Should I select "sync music" on the "old" device? If so, what does that do and what is the next step for adding those exact songs to my "new" device? Whatever the answer, please spell it out for me. 😉 Thanks!