There is a stigma around muzzles. What people don't realize is muzzles can save not only their dog's life but dogs' lives around them. Some dog bites could have been prevented if the dog was properly muzzle trained. Muzzles are like dog crates they could either be a security blanket or a punishment. It is all based on how the human uses them. I suggest training your dog to a muzzle even if they are not aggressive because even the sweetest dog can bite when injured. Your dog could be muzzled at the vet, groomers, or even by a pet sitter if it is deemed necessary for the safety of others. Having your dog view the muzzle as a good thing puts less stress on your dog when it has to be used. I recommend the groomer's/Mickey Mouse muzzle because the front of the muzzle is open where the dog can take small treats or water but is not able to chew a bone. I don't recommend basket muzzles because people fear dogs when they bark, and even more when barking with a basket muzzle on. These muzzles also make it very difficult to provide training treats through.
Positive training for the muzzle:
I encourage the technique called "shaping" because it encourages your dog to use its brain and helps them establish problem solving skills. To begin shaping you must train the clicker. The clicker is "charged" by clicking and giving the dog a treat over and over for about 10 minutes. I suggest always charging your clicker even if your dog knows the clicker means a treat will be coming. The clicker is a marker that marks a behavior as soon as you can register in your brain the thing you wanted is being shown. Here's an example using the muzzle. Our goal is to have the dog willingly put his/her muzzle in the muzzle because he/she wants to. Start off in an environment that is distraction free. A room that doesn't have other things the dog can pay attention to or play with. To shape the muzzle, I start off by putting the muzzle on the ground. If the dog does anything to the muzzle I click and reward as fast as I can. This includes looking at the muzzle. In a truly distraction free environment, and the dog never having seen a muzzle before, the dog will naturally become interested in this random object you placed in front of him/her. Again, ALL interactions with muzzle must be clicked and treated in the beginning. When your dog has figured out that looking at the muzzle causestheh click and treat up the stakes. Only click and treat for movement towards the muzzle now. At any point if your dog is no longer trying to figure it out or not succeeding every few minutes, you will need back up a stepini the lesson. Once your dog is successfully moving towards the muzzle repeatedly begin to only click and treat for distances that are closer than your original movement. Do this until the dog touches the muzzle. Any touch to it should be rewarded, even slapping it with their paw. If it has been more than 15 minutes at this point, go back to the step the dog was last successfully completing and repeat it 10 more times. Then end the game with "game over" or "all done." You can repeat this process multiple times throughout a day but it's better to have short and sweet then long and frustrating. Now the dog is touching the muzzle reliably. Start increasing the stakes by only accepting when his/her face touches the muzzle. Again, once reliable start accepting only nose touches. Your dog at this point knows that if she/he is not getting clicked and treated that he/she isn't doing what you are looking for andwilli try new things. I would have the muzzle in the direction that the dog would be able to put it on at this point. Raise the stakes once the nose is touching the muzzle consistently. Now you are looking for any movement toward inside the muzzle. You guessed it, when repeatedly successful start rewarding for shorter distances until the dog is placing his/her muzzle in the muzzle. Each time you repeat this lesson your dog will take less time through each step to a point where he/she puts the muzzle on the second you put it on the ground. At this point is where you can add a cue such as "muzzy up" or "muzzle on." Make sure to have excitement during the whole process and everytime he/she wears the muzzle. I like to give a treat everytime I have him/her wear the muzzle so it's always seen as a good thing.
Congratulations! You successfully accomplished one of the most important lessons your dog will need to learn. You can use the same method to train other things like sit or stay. Don't leave the muzzle somewhere the dog can put it on whenever he/she pleases.
Never use the muzzle as a punishment for barking or biting. Always put the muzzle on before doing something that offers the opportunity it bark or bite.