I'm trying to implement an approval process in JIRA. Right now, I'm going with a multi-user picker custom field, where I'll record the names of everyone approving the issue. What I'd like is to have an email sent from JIRA to the users that are mentioned in the custom field. I've set up the "approved by" field to show on a transition screen when the item transitions to "approved," so I have a transition that I can add a "fire generic event" step to. However, I don't know how to say "fire an event that notifies only the people in this custom field".
Any ideas how I can have people added to a custom field get notified to that effect? Add them as watchers? I'm looking for something similar to what happens when you @mention someone in a comment.