Discogs and Fanart for artists on a compilation manually tagged

I have a VA album (compilation) unknown by Musicbrainz, so had to manually tag it with mp3tag. Therfore there are no MBIDs and the scraping process does not pick up discogs and fanart. Since those look very nice on screen for the other artists, I would like to “add” them without going through a multistep work for every artist.

Is this possible and how do I do it?

Rgds. from Vienna, Austria,
Heinz