Being consistent is very important in training your dog. Practicing consistency means that you need to use the same word for a certain behavior all the time.
Aside from that, you should also be consistent punishing him for his bad practices, so that he would be able to put it in his mind.
Only one person should give a command at a time
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Your dog would have a hard time telling which person to follow, if two people would give him conflicting commands at a time.
Even if the command is the same, it is still best for only one person to give it at a time.
This way, your dog would be able to pinpoint which person and command to follow, instead of getting confused.