I may be able to help you as I have about 27,000 mp3s on my D drive, but only want about 1700 of them at any given time loaded onto a USB stick for car playback---these are my favorite 1700 songs out of the 27,000. I am constantly acquiring new songs and new favorites, so both D and the USB stick vary over time.
If you have ripped 3000 CDs, I am guessing you have a minimum of 3000 folders.
That presents a browsing problem. How can you browse 3000 folders containing 30,000 songs, looking for just 500 to put on an mp3 player? The mouse or keyboard clicks alone would be in the tens of thousands. I assume you'd need to eyeball the artist and title to decide if it's a member of the select 500.
I'd probably do a one-time copy of all 30,000 songs to a single folder. A copy, not a move.
That way I'd only have to scan the contents of one folder with my eyes. Just scroll down the folder of 30,000 songs and select the 500 you want to copy to the temp folder.
Any new CD rips can be copied to the 30,000 single folder or the 500 temp folder as desired.
There might be some other way to browse from 3,000 folders without driving yourself crazy, but I haven't come across it.
You'd need a way to copy all of your 30,000 songs into a single "flat" folder.
There's more than one way to do that, but the easiest I've found is to use the "Everything" search tool from voidtools.com.
You'd install it and then do a search for .flac, which would presumably bring up your list of 30,000 songs.
Highlight the entire list and right-click for copy. Then navigate to a suitable location and paste. All the files will be copied into the location FLAT into a single folder, without the folder structure used on the originals. Once that's done, just scroll this single folder and select what you want to copy to the select 500 folder.
Storing copies of 30,000 FLACs might take a few hundred GB. My 27,000 MP3s take up about 110 GB and I think FLACs are 2 to 3 times as large on average.
You might find it more useful in the long run to categorize your songs by genre and/or artist rather than album, but that's an individual organizational choice.