Please do not use those collars, even the air or water ones. Yes, they are now legal, much to my chagrin. (To be clear for anyone reading casually, citronella or other chemical collars, as well as electric or acoustic collars remain illegal. )
But automatic punishment collars are nonetheless wholly inappropriate for your situation.
In order for punishment to be effective, especially punishment using primary negative reinforcers such as pain and fear, the timing of punishment must be carefully controlled. If timing is off, the dog can associate the punishment with other actions, or variables completely unrelated to his actions, thus learning something you might not have intended. If one chooses to use negative reinforcers one must be on the spot at all times in order to control the environment, and thus associations and learning.
One should never use an anti-bark collar when the dog is left alone. (And I strongly believe that one should never use them, punkt.)
Because primary negative reinforcers such as pain and fear are so intrinsically strong the dog quickly ingrains what he has learned... Thus making it very difficult to 'unlearn' should he make unintended associations.
A quick example:
Fido is home alone, looking out the window, wearing a collar. A bird flies by, Fido barks. He gets hit with a blast of air, frightening him. Instead of the intended lesson (barking causes unpleasant sensations), Fido associates the appearance of the bird with the unpleasant sensation. Another bird flies by, Fido barks, is hit with an unpleasant sensation, Fido 'reasons' that birds cause nasty reactions. He begins to be afraid of birds... And soon Fido is unable to go out on a walk for fear of a bird appearing on the horizon.
Dogs often make associations we do not expect.
If a dog is left alone, punishment is a very dangerous tool because you have no way of controlling the association between the action, stimulus, association, and response.
Additionally, actually most importantly, you mentioned that your dog is already anxious. Punishment is never the way to go with a fearful dog, as punishment relies on creating additional fear as a deterrent. When punishment is used with an already fearful dog you run the risk of opening the door to a whole raft of behavior problems.
Specifically with separation anxiety. The dog is already uneasy with being left alone. Now you put on a collar. Bad things start to happen when that collar is on... Which happens when you leave him alone. Ergo, the dog soon comes to see being left alone as an even more frightening situation. You have just ingrained the separation anxiety, making the problem worse.
Punishment/ negative reinforcement should never be used with a fearful dog. Automatic punishment collars specifically should never be used with a dog with separation anxiety.
Further, automatic punishment collars by itself will only suppress symptoms, they do not cure the emotion that drives the behavior. The fear is still there, but the dog is unable to express his fears. This can lead to the dog shutting down, and again, a whole range of behavior problems can emerge in that case.
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Re-training a barking dog is a time consuming process, one that requires the owner to be right there, on the spot to address each and every incident, consistently. But it is time well invested, especially in Switzerland.
A deaf dog is a special case. I have had a profoundly deaf dog, as well as many oldies who lost their hearing with age. I'd be happy to chat with you further about working with deaf dogs, perhaps via PM would be more appropriate.
As you might guess from my many posts on the subject of training, I only use positive reinforcement. I believe this is not only the most humane way to train, but also the most effective. Positive training teaches a dog to make good choices; while it may take longer to train, in the long run your job becomes far easier.
Rather than going the collar route, to buy you time to work on getting the barking down to 'Swiss standards' , do you have options for short term care for the dog? Daycare isn't expensive, or look for a sitter who can care for the dog while you are settling in.
Dog ownership isn't always easy in Switzerland and often means compromises, adjustments, and expense in order to give our dogs the environment they need.
Wishing you and your four footed friends an easy transition, and hope you all enjoy your Swiss adventure.