Remind me of CB's breed! Dogs with HIGH pray drive are harder to control in this kind of thing. Also, what kind of "tells" are you getting from him?
It's always best to stop the behaivor the split-second it starts? When Patchs starts barking at someone, I react at the same second that the first bark comes out of her mouth. I use the word "ENOUGH" followed by, "WATCH UM" .... in the beginning I would sit by her at the window and have my hand on her back. When she barked i'd tell her NO and then WATCH UM. When she understood that she was NOT to bark, I changed the word to "ENOUGH"
I don't mind her telling me that someone is outside, I just want her to bark once and then be quiet.
It's worked well, b/c now if I think I hear something I just say, "WATCH UM" and she'll go to the window and looks to see if someone is there.