As always, I want to do my caveats. Surely you know by now that stuff written on the internet is just opinion, but … without this caveat, that, hey, I’m just this one guy, after all, I worry you’ll think I’m an expert of some type, some sort of guru papered with a “PhD in dogs” 
…
Not at all, of course, but I’ve introduced four dogs recently and I was trained by a Rottie rescue owner (he had three living together, two who wanted to kill each other at first) and a friend with a couple of Boerboels and other dogs and lots of kennel experience. Before I get into any of my thoughts, let me talk a second about the advice you read on the web: Mostly, the theory is, you get together in a bright green park, using various techniques (fences, neutral territory, parallel walks on lead, etc) you introduce your dogs, give lots of treats and praise, and after a couple of corrections and a couple of minutes they’ll play bow and be best friends and your job will be done — bring them home and they’ll curl up by the fireplace together.
The problem with that idealist theory is the correction point: If we are dealing with a couple of smaller dogs, if they decide they want to start a scuffle it’s fairly easy to reach in between and pull them apart and give them the Cesar Milan tsssssk!, but if you’ve ever tried this with a Boerboel, it’s a slightly different, more intense issue. However, this image of a scuffling Boerboel in a park may make you think of all sorts of chaos and kids running from the park, letting go of balloons, people running away, my god this is too much for me, it’s all going to be too hard … Stop. It’s okay. You can do it, if you’re willing to take this way more seriously than some of the rescue sites will say.
Just note that the above meet at the park could – and often does – go really well, as some dogs are social butterflies and just love meeting new “people” and thus a lot of this will be overkill. This is based on a couple of dogs I have known who came into a home wanting the other dog gone, maybe even dead — and moving up from there to sleeping on the bed together, using each other as pillows, while I’m typing this (actually, one just rolled off and woke up on the floor, surprised. 
).
1) First off, give each a safe place.
The “new dog” will be stressed. This house smells owned. I don’t belong here, etc. Set up a place where they can feel safe when things become too much. Feed there, etc. and don’t let the other dog go there yet. Eventually that’ll be fine, but off the start I’d say keep it safe and his or hers only. This place should have a view of the house, so that he or she can watch the flow of the house for a couple days at least before coming into the flow.
2) Be prepared. Predict, don’t react.
You are like a director. You are setting the scenes. Checking the exposure. Calling for makeup. Okay, not literally, but you sort of playing that role, making sure that all variables are under control. If you’re getting two dogs to interact, take a look around. Are the doors locked so that kids don’t run in crying? Are you using a baby gate too soon, where a grumpy 150lb dog may lean against it and pop it off the hinges? Did you leave food on the floor? Have you considered everyone’s mood (anyone need to go out? hungry? etc.) If things get out of hand, do you have a broom around, or a pot of water, or anything to break up a scuffle?
By preventing, you are both decreasing the randomness of a scene, and you are increasing the chance things will go well, and thus you’re projecting a lot more confidence.
3) Are you going slowly? Well that’s too fast!
There’s no harm in going too far, too slow. My friend Craig told me his three Rottweilers started out with two who hated each other. He said this:
I chained them up carefully so they were just within a foot of each other but couldn’t hurt each other. Within 30 days they were best friends. Any aggressive dog would be fine in 30 days.
I had a fearful dog once that took more like 45 days, but this is the same dog that I learned off of, so he had to tolerate me not doing any of this stuff in an organized fashion until I realized what wasn’t working. Poor guy.
4) Avoid forcing tentative dogs together. Go at their pace — if you have to go that fast.
Oh, I regret this mistake. We lived in a century home and the front room was tight. REALLY tight. Dogs who are unsure like their space. I could barely stand in it with the dogs while getting the door open, getting my shoes on, etc. thus the dogs were jostled into each other. A terrible plan. Ended up with a scuffle in that tight space that caused injuries to all three of us, simply due to bad planning. While I corrected the instigator, really at that stage in their introduction, I was the one who needed the correction: They were not ready for that, at that stage. I knew that, in hindsight. In my more recent dog experience, I could at a glance at a room and say “that chair will need to move for two weeks, so that the dogs can move in and out without trapping each other”, etc.
5) You are increasing challenges, but eat an elephant a bite at a time
You are testing them. Sure they got good at meeting through the closed door, but how about the baby gate? Okay, a week of tail wagging through the baby gate looks great, how about outside in the yard? Etc. Just try to increase the pressure slightly, but only when the old routine has become routine.
6) Get two dogs stable first, then get another two stable. Don’t introduce one new dog to multiple old dogs.
Pick the most social dog of your existing pack, and use him or her as your “crash test dummy” — carefully. Then, when those two are through the program, put him or her away and get the other introduced. Two dogs are stable, more than that is a bit too much like a circus for all but the much more alert dog owner.
I guess this is a start, anyway. Eventually, you can get to the point that you can lock all of your intact, dog aggressive dogs together in the car (yes, on a cool day!) and go in the office and come out four hours later to no drama and tail wags.
If anyone else has any thoughts or ideas, please tell me or add them to the comments section! Also, I posted a bit more on advanced social training elsewhere in the blog, which should be looked at as well as it comes at this via another angle.
Thanks again,
Ron
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