Here's a precious little clip I found a few days ago, "Maxie and Fooh Fooh's First Play Session". A little history is in order for this one.
When we brought Max home at 4.5 lbs, Fooh Fooh HATED him. Growled. Snapped. Lunged. What you might expect of a 40 lb., semi-wild Dingo, used to being the only dog in our household. We thought "OMG how will this ever work?" We kept them in separate parts of the house, in different yards. At night, Max slept in our bed with his leash on my wrist so he wouldn't jump off, Fooh slept in his accustomed place on the floor at the foot of the bed, now leashed to the dresser so he couldn't jump up. Watching TV at night, Fooh was leashed to John's arm, Max to mine, or Max was in a crate with Fooh circling around, growling. After a week of this with no improvement, we had resigned ourselves to living this way permanently. Seems ridiculous now, but there it is.
Then I got the bright idea from Cesar Milan, The Dog Whisperer, to walk the dogs together each night. He says they form a pack by walking together. At first, John was up ahead with Fooh and me trailing 6' behind. Then Max and I circled wide around and took the lead. Gradually, on each walk, we shortened the space between them and within a few days, after 10 minutes, they could walk side by side, me with an ever watchful eye and ready to jerk Maxie out of Fooh's snapping jaw any second.
Within a week of doing these 20 minute walks through the neighborhood streets, they walked like chums from the start of the walk and I finally felt confident enough to put them loose together in the living room. This little clip (Maxie about 7 months, 5 lbs.) captures the result:
Now, 3 years later, all my dogs roam loose together in any room I'm in, unless there is anything resembling food around. Fooh is very jealous of food. I still separate them when I leave the house, and of course, I still never leave Maxie or Willow outside alone, with or without the big dogs. They look too much like prey to the hawks and owls that frequent our air space, a fox or two have been sited in the woods before, and the big dogs can play rough.
I now believe totally in walking new dogs together to get them to accept each other quickly. When I start up a new class, first thing I do is have all teams walk with me around the perimeter of the field. By the time we've gone around just one time, all the dogs seem to be friendly, focused and settled in, not to mention warmed up and ready to learn.
Upwards and onward!