There are many ways to go about stripping and retagging the files. Depending on what operating system you are using, the software will vary.
I convert to wav file to strip the tags as it is fast and then I can set the compression level for the flac when I re-encode (plus it tests for errors while doing it).
However, you do not need to convert to wav file to strip the tags - just a good tagging program (dependent on your operating system).
On linux, I use EasyTag and Qoobar (Qoobar has more options available for composer, performer etc). However, flac tagging is a pretty open-ended system. You can pretty much make any tag you want as they follow a very simple format:
Plus you can have multiple fields of ARTIST or TITLE or COMPOSER or whatever.
Just bear in mind that most devices and software will only recognise certain fields: eg. artist, title, tracknumber, year, albumtitle, etc., as most are designed for "popular music".
If you need more info regarding their use - search for "flac tag" or "vorbis comments" - they are the same.
For your software needs, just search this thread - I'm sure there are many recommendations for your operating system.