This is actually a great tip. I usually rip first and then add, but this is probably a better workflow because the files will be tagged right from the start. Thanks! I'm sure a how-to would be very helpful.
I use isrcsubmit.py to submit both DiscID and ISRCs before ripping a release. Unless my memory is completely off, Picard will also fetch the ISRCs attached to the Recordings and embed those into the tags.
Thanks for mentioning this script. It's nice to have. I didn't knew that this exists. I will use it from now on.
FWIW, if one uses foobar2000¹ to play their CD², there is no need to even rip as it can tag the CD itself directly (tags will be written in your local cddb folder).For tagging from MB, you can use foo_musicbrainz (it will unfortunately use recording names instead of tracks, but it’s otherwise quite good plugin).