i haven't used it on my yorkie but have used it on other dogs in teh past. if trained with it correctly the dog will respond. they don't like the smell. The collar should be positioned on them so that the spray goes in front of them, it shouldn't hit their face so make sure the collar fits right.
its hard to train them not to do something when your not home. There are also products that emit a high pitched sound when your dog barks.
Ultrasonic Dog Bark - Home & Garden - Compare Prices, Reviews and Buy at NexTag - Price - Review these things can be placed on tables and not on the dog so they don't have to wear one of those collars.