I'm not sure what other lands require. In Australia that must be covered in the Operations Manual. I use throttle below 1000'agl and mixture above. The Ops. Manual says 500' just in case some Lawer wants to argue about a few feet. I think it is better training not to be consistend with the failing method you use. Near the airport and above 3000' I also secretly turn of the fuel. Nearly everyone looks at me with utter disbelieve, does nothing, and asks "how did you do tha". A lot of students get the idea that the engine ill only fail 'when the instructor does something'. I'm worried that we are training students that are proficient in 'simulated failures' and not proficient in real ones.
Some time ago I did an instrument renewal for an instructor. Turning inbound on the NDB I failed an engine. He handled it perfectly. A bit later we did some unusual attitudes. He was in the process of loosing control of the aircraft when he asks me "what are you doing". We had a real failure and he was lost. (turned out the needle valve in the carby got stuck). I aggree with sweet surrender "how would you feel if one of your students killed themselves because you did not train them to the best of your ability." How would you explain that to the Lawers and insurance company.