Decoys should be carefully selected, trained to the highest possible skill level, and given periodic refresher courses for maintenance. The extra time and resources invested in training decoys will not only yield better dogs, it might prevent many future handling problems. A good decoy is worth his weight in gold. Certainly this has been done in the past and sometimes is the only available option, but is not the best approach. It's not even a good one.
Any fool can put on protective gear and take bites, but being a good decoy requires sophistication.
First, the decoy must be schooled in canine communication. If he cannot read the dog properly, he cannot respond correctly to what the dog is telling him. For instance, there are times when the dog's confidence level drops in the middle of a drill. By the time the trainer can tell the decoy to release pressure, signal insecurity and move away, it is already too late for the dog. The decoy must react instantly and correctly to such problems, then consult the trainer about what to do next.