What you can do is first set up a smartlist to include only one song from each album. Then
1) Select all tracks and right click and run. You are going to have to manually choose each cover however as there are often multiple hits per album. Your look up time will be substantially reduced however. You will get a box that says save and continue
2) Afterwards you would have to run Cover Art =>Save Cover art to external locations (keeping the selection on the tracks)
3) Lastly you would then have to select all the tracks from each album and run Cover Art=>Quick find in File/Cover Art directory.
Note: a) have not done this since version 17 or so
b) my cover art config is having a folder.jpg file in each album folder (this is probably necessary)
This is less tedious than it sounds, however I found this an enormous waste of time because most images I look for must be minimum 600x600px. And often the database either doesn't have the art or the art is real crap, low res. Would recommend trying 100 albums (or albums with Artist starting with A and see if it is actually worth it.
Also you would be putting a strain on the database if you are scrapping 5000 cds, so maybe limit it to a couple hundred a go for other people's sake.