I've used the citronella collar with varied success. Used one on a dachshund we had years ago --- she learned not to bark when the collar was on.
However, a number of years later, I had a cocker who was a problem barker = he had severe seizures occasionally, and I really think there was brain damage involved.
He learned that if he barked enough, he could empty the cannister on the collar and then he could bark to his heart's delight.
With the vast majority of my dogs, I've had just as much success with a spray bottle filled with water, set to emit a stream of water (not mist)... so you can get them from across the room.
The problem child who learned to empty the citronella collar, would come up to me when I spritzed him, squeeze his eyes shut and bark... as if to say, "go ahead, take your best shot." I had to laugh at him with his face all scrunched up.
Bottom line, with the "normal" dogs, I had better luck with the spray bottles. I kept them sitting all over the house, so one was always within reach. It got to the point I didn't even need the bottle. I'd point my finger at them and make a shh shh noise, and they would shut up.
