iTunes Match does not work well (if at all) with manual tagging. I've heard of users who have lost all their metadata. Apple decides which metadata to use at all times. This is even worse than the iTunes Advanced Preferences setting 'Keep iTunes Media folder organized' which makes it impossible to to maintain filenames and a sensible grouping of compilations into a single folder.

There are lots of taggers which claim to fix an entire collection with the click of a single button .... Yate does not claim to do that. At least we don't push it. It is possible with digital fingerprinting for Yate to find best matches to MusicBrainz which can also lead to Discogs. The issue is that digital fingerprints are far from perfect. Manually searching MusicBrainz and/or Discogs will give you results that you can vet and therefor be guaranteed that it makes sense.

The same is true for artwork. Matches can be made automatically but there is no guarantee that they will be correct.

When I was updating my collection about two years ago I decided to fix the artwork manually. I used Yate's Auto Search for Artwork function to get high resolution large images. When I couldn't find anything I used the Google-Large-Image template to find artwork. Think of it as doodling 🙂 Again this is just my opinion. I'd rather do it slow and pull stuff I like.

There are actions supplied on the Resources page to attempt the automatic methods. Calling some of these actions from a batch process is possible. Again, I'd personally recommend trying stuff manually first.

Whatever you decide, you will have to decide what you want to do with iTunes Match first. You could fix the metadata in a pile of releases and have them mess it up all over again 🙁