We have one of the spray type collars and they do work well as a training aid. They can be expensive on batteries though, so you wouldn't leave it turned on all the time - which means that often when you might want to use it it's no good because it's not turned on.
As you know, I have two Beagles and they are quite vocal dogs. They do that annoying 'warning barking', it's not an aggressive thing. Mine always bark at strangers coming in the house and at people walking past the house, but apart from that they're not too bad now. (Although as I write this Harry keeps coming in and crying to me because there's a chicken carcase in the kitchen he thinks I should give him)