I have never smacked my dogs either. One of my dogs would bark constantly and I would simply use a bottle to spray water in his face. That combined with positive praise when he was quiet and a week later the barking had stopped. I know you can't compare this to a child but it goes to show that I didn't need to use violence or a power trip to get him to do the right thing.
Just to clarify, (but getting OT) smacking and spraying with a bottle are both punishment techniques. The difference is that if you use smacking the dog is focused on you, knows the punishment comes from you, and may not make the connection between the behaviour and the punishment. The waterbottle is used while the dog is (presumedly) looking at whatever is stimulating it to bark and not you and is more likely to make the connection (and not think it came from you). If for example, you went up to the dog and then either smacked or sprayed it would have the same effect as the dog is then focused on you and won't make the connection between behaviour and punishment. Both are negative for the dog and really aren't very different. Again it is about making the dog think of the appropriate cause and effect - that the barking causes the spray and not that the owner having a spray bottle causes the spray. IYKWIM?

(but I actually don't agree with punishment used in this context. Just wanted to explain a bit more from an animal behaviour POV)