People's collars are not actually being disabled for this exercise; they're doing the enchanting exclusively using tools. This is the sort of thing that's more awkward and expensive than just having a regular wizard do the work -- economically speaking -- but perfectly possible, just like doing a factory assembly job via teleoperated robotic hands would be feasible on Earth, and it does serve to teach the skill.
The vibrators have a physical component! Lesser magics do go easier with a physical anchor! It's the shape that it needs to be to fit its target, plus an ergonomic handhold for the assistant.
This physical compenent is already provided; manufacturing that part isn't what they're trying to teach today.