Always enjoyed my IT training days.
I had two main methods to make it run smoothly.
1. Identify the smart-arse know it all ASAP and set a trap for him in not giving him some important info (that would have been given later in the course) so he screwed something up when charging ahead. That always put them in their place.
2. Always go at the pace of the slowest trainee. Yes it may annoy the smart-arse but it meant that the 20 people that turned up all went away trained and knowing what they were doing. Seen way too many courses where the trainer is a lazy arsehole that just panders to the two smart-arses and leaves the rest behind.