I have given editor and moderator roles to my very best subbers, the ones who rarely make mistakes and I know that they know the language very well.
As for subbers, I try to include 2-3 inexperienced ones on every team. I believe it is good because 1) you never know, they might be a hidden gem, as it has often happened 2) one has to start from somewhere and 3) the good ones are not always available, sometimes they will leave Viki because of X Y Z reason, so you have to renew your pool of collaborators.
Seeing that there were some common mistakes that all newbies - and many experienced ones - make, and that I wasted a lot of time in correcting them again and again, I created a course for Italian subbers.
Of which details are here in English and here in Italian My Italian Subber Training Project (both beginners and experienced)
I am now starting my 7th group and I’ve had some wonderful experiences. Some of those people left soon, because they didn’t have the time or inclination, some others stayed until the end and became very good subbers I often work with, others yet missed many lessons and they stayed mediocre, still with some more knowledge than before.
I also learned a lot in preparing and in conducting those courses. And with every new batch I learn more.
It’s called a course for subbers but in reality it also teaches editing, because, of course, everyone is first and foremost an editor of oneself, and because we do together editing of the work of all the other participants, trying to find out together the best way of translating something into our language.
And there are several moderator skills involved as well - for instance how to make a project Google sheet, how to save subtitles, the basics of how to make a cover page etc.
One of the ladies that finished the course, wrote to me, seeking advice on various matters, when she first became a moderator and when she became a CM and we had a thick correspondence via Messenger. She is now one of the leading figures of the Italian community and I love her!
And of course I always gladly share tips with anyone who asks, either here on Discussions or by private message. As do many of the other old-time volunteers in the community.
I’d be more than happy to help anyone else who would be willing to try to create such a course in their own language.