I stumbled upon the entry for Dark Sky but on closer inspection I’ve discovered it’s actually two different artists with the same name 1) a German metal group 2) a London based producer,
I’ve created a new artist entry for the London producer but what’s the process for separating all their releases and the like?
They need to be edited to have the correct artist 
there’s no faster way, generally.
I see, does that mean I should make the separate entry based not on the annotation but reducing the number of relationships that need to be edited or reassigned? In which case it would make more sense for the existing entry to refer to the London producer and I create a separate entry for the German rock group instead.
Given the London producer Dark Sky has more releases and links associated with the existing entry than the German group I decided to create a new artist entry for the latter https://musicbrainz.org/artist/cb79ec32-a5a8-480c-a3b5-9dc17157fe9e and have raised edits to correct the handful of releases relevant to the German band
Anyway, the initial MB artist was created for the producer, not the band, so it’s a perfect choice.
https://musicbrainz.org/edit/12565988
https://musicbrainz.org/edit/12565990
Ha, I even added the producer’s EP’s as far back as 2012! 
(actually it was a trio back then)