When I was training with others we would give each other a couple magazines and randomly place a couple snap caps in the magazine. This way the shooter would not know when they would have a misfire.
Interesting note about this is when people know in advance that they are going to hit a dummy round they tend to shoot differently. Best case I can think of is to shoot with someone using weapon that uses the same magazines. Add dummy rounds to magazines here and there but not all. Put the magazines in a pile and mix them well so neither of you know whats coming up. Then shoot casually. Make corrections as needed. Maybe I am different but I think if doing this whie shooting casually does more to train that specifically training knowing you are going to get that douumy round “now”. Just add some in to everyday routine training and learn to cope without the pressure.
You can later add the pressure of knowing you are going to get a dummy round but since you are already anticipating it I think it is not as effective as a training tool.