There are plenty of tools for tagging Mp3 files not so many for Tv Shows and Movies.
With iTunes you can tag to a certain extent within iTunes but it isn’t great. So I looked at other options and iSubtitle is an interesting one.
It’s prime purpose is to allow you to mux in softsubtitles into movies and tv shows, it is pretty quick but the demo version limits you to 3 minutes and adds extra subtitles into the stream for around €20 it is pretty good value. There is also roadmovie which can do hard subtitles and a few other useful bits.
ISubtitle even unregistered can write the metadata to mp4 files (well formed ones anyway). However there is a bit of an issue iTunes will rewrite the filename as the episode title convention tends to be series-name season episode title. So you have a choice to make do you want this in your episode title or not?
not looks good in iTunes but with makes it easier to identify the file.
within the file would be season series episode number anyway so… you may want to rewrite the title or not.