I know that there are many trainers who use focus mitts as a method for developing cardio, but many of the coaches/trainers who I respect seem to reject this notion and feel that the purpose of focus mitts is to develop technique. Assuming that this is valid for the moment, how does one effectively use focus mitts to help students develop technique? What should be focused on (combinations, targeting, speed, etc) and how is this generally done? How should the trainer hold/use the mitts to maximize safety and efficacy for the student?
There's nothing wrong with using focus mitts for technique or cardio. Although, you'll have to get the technique right first before you use the mitts for a high intensity workout. Probably what these trainers are trying to say is that it's easier to have a fighter wail on a heavy bag for cardio than to punch themselves out on focus mitts. They're likelier to miss with focus mitts, and therefore will be more focused on accuracy and not as focused on putting oomph into their strikes.
To develop technique: