
Have you tried leaving the house with a dog/dogs then returning
imediately, before he has chance to react? Repeatedly do this, then as he is becoming familiar, increase the time spent outside.
So it would go something like this:
Leash dog/dogs, step out of door. Close door (
if your barker remains silent, otherwise don't even close the door). Step back inside. Unleash dog/dogs, go pop the kettle on (or anything not remotely related to a pre-dog walk routine) & repeat.
Once your barker is getting the hang of the fact that you are returning (before he has chance to react), increase the time spent once outside. (close door, take one step away from door, then go back in).
Then increase to two steps from door etc...
If he is getting very unsettled with you just leashing up the other dogs, start off by not even leaving the house or approaching the door, simply leash all dogs, stand there for a couple of seconds & then un-leash them and repeat.
He is obviously not happy being left at these times, so the same approach you would use with a seperation anxiety problem will do the trick.Evry time you leave him and he barks, it only goes to make his problem worse, so you are best off avoiding leaving him for now, even if that does mean the other dog (that he doesn't get on with) is going witout walks for a little while (take barker on both walks for now as changing his barking reaction is going to take a while). You could do something else with that dog (the one being terrorised by barker), at home, to keep him stimulated and exercised (hide & seek, extra training, fetc etc...).