John Howard from MS wrote a 5 page article on how to grant remote admin rights using the Hyper-V MMC to Hyper-V servers that were not in your domain, e.g. in an un-trusted domain or in a workgroup. It was 5 long pages of detailed instructions where anything could go wrong. It was quite off-putting.
He’s just shared a new tool that will do the job for you. HVRemote works quite simply, you just tell it to add or remove a user’s admin rights. Well done John!