You could take a look at the python script I’ve written to accomplish this task for my folders since I found it to be impossible/impractical to do in Mp3tag itself. I’ve described how I use it as a tool in Mp3tag in this unfortunate thread.
WARNING:
You should only attempt to use it if you’re comfortable with the command line and have a basic understanding of python so you can glean what the script will do or ideally adjust it to fit your preferences/needs.