Automatically tag all genres

My collection is a mess it has mp3's from the 90s still today and over half my files are loose mp3's without an album.

Yesterday I did a little bit of cleaning up giving some songs titles and others artists

Media Monkey is fantastic at figuring out names and stuff from really messy files.

So however what I am now stuck with is a huge collection of somewhat correctly named songs from artists.

so far it's all great but what I really want now is the genres. not 100% correct but still better than the 60% empty and 40% laughable I have now.

So what I want is for mp3tag or other application (if you know a better suited one) to simply for each of my track scrub some online database and get the genre.
If it does not find the specific song, then maybe finding the genre for the artist overall and putting that on the song.

I have some 20 000 songs (after clearing duplicates yesterday) so now the question is how on earth can I get it do update the genres of my 20 000 songs (and update more info if it finds more)?

I have no interesst in doing this manually in any way as my collection changes to often and it's just not worth manual hours... I do not demand perfect result, just better than nothing. of course the better the happier I am.

I did find a script for last.fm but since thats tagged by users it seems that mostly it's tags like "songs i like" as a genre. What I want is fewer genres so I can get a good playlist from selecting just rock, or pop or chillout.

so i dont want genres that are like, "mellow chillout" or "groovey stuff i listen to in the kitchen"

And I know most people will say genres are subjective and I have to name them, but as I said I just want better than nothing really and besides I don't know how to categorize half the songs out there.

Thank you all, if anyone can help my I'd really appreciated it!