I'm sure you're good at doing it, and demonstrating it to others. However, if it had been established that the guy was a problem, one of your managers probably should have done the training, or at least been present for it. That would've accomplished two things:
1. Made it clear to your coworker that management was aware of a problem, and that this was his remedial training/gentle warning. The way you wrote that, made it sound like you just called him over and started trying to instruct him. Problem employees often don't take kindly to direction from more experienced peers. It's why they aren't employed for very long.
2. The manager can attest he was properly trained on how to use the equipment, so that they can start keeping a record. That will be handy for when he gets fired next month because he still hasn't learned his lesson.