Here is how I reduced 46k songs to 18k for iTunes Match.
On my PC I used Media Monkey. It’s very efficient to use when making playlists. I built playlists of must have party songs, disco songs, AC songs etc. it takes a few hours but it is still easy to use.
I then created a new directory on an external drive for iTunes. I removed my old itunes lib so itunes was empty. I went into preferences and told itunes to copy all songs that are imported to this new directory. Now I exported the playlists I created in Media Monkey to the new itunes folder. (I also tagged each file exported with a note in the comment field that said exported, very easy to do in media monkey as a batch).
Now in itunes I imported the playlists. iTunes copied the songs to the new directory as it imported the playlist.
By doing this I eliminated many songs I never need access to. I don’t need Neil Diamonds entire hits album or the entire Promo Only series for each month so I only copy what I needed.
Back to media monkey I searched for songs that weren’t tagged as exported and now looked again for songs I missed the first time. If I found some they were saved in the same playlist I initially built, exported and then imported into iTunes, the added songs showed up.
I highly recommend Media Monkey for controlling your music. It has great features and can really help to sort out your music.