Nana and I had a houseguest for about a week while I dog-sat for a guy who was going to Tokyo. Nana had met Woodley a couple of times before, and they played together fairly well, so I figured they'd get along well enough.
I picked up Woodley on the way home from Kendo class, so it was well past dark when I got back home. I let Nana out, and let them tear around the yard a little while I unloaded the car, then put them both on leashes and did a little jaunt around the trails to help reinforce who the pack leader is for them. I also made them both stay until I was in the door, then let them come inside. I also started teaching Woodley a couple of new tricks, having Nana run through hers as well. Nana was very jealous about me giving Woodley any treats or attention- I kind of figured she would be, and was looking forward to working on this with her. Over the course of the 6 days Woodley was here, she did get better. After a few days I didn't need to be standing between them, keeping Nana back mostly with body language. She's still possessive, but not quite so aggressively as before. By the end of the week, I could give them both a treat, and Nana wouldn't try to take his. Also by the end of the week, I could put both their food bowls down and not worry about them trying to steal from each other. I continued to make them both wait for my invitation to go in or out of the house rather than just booking out the door the second it's opened a crack, as well as made them both sit and stay before they could eat.
They had a few moments when they were outside playing where they got a little rough and yipped, but that's just part of dogs teaching each other appropriate play. It never escalated into an all-out fight. Woodley's larger, younger, and more energetic than Nana, but was good about letting her chase him sometimes. Woodley also responds better to verbal signals. If he started running off, just calling his name was enough to get him back. Nana has selective listening, and will ignore you if she thinks something else is more interesting. On the other hand, Nana is a little more clever, and learns things faster.
One of the mornings I took them out for an hour-ish walk, we got caught by a passing shower torrential downpour- it was bright and sunny before and after. While in the midst of the sheets of rain flowing down, we passed by a farmer's house, and the farmer in question was standing in his entryway looking out. He offered me an umbrella, but I held up both hands, fully occupied with a dog leash each, and he smiled at me as I went on my way. It wasn't so bad, I was just wearing what I refer to as my "dog clothes", the ones for being out in the woods or playing with the dog, the ones that it doesn't matter if they get rained on, ripped, torn, whatever.
Now that Woodley's been back home a couple of days, I think Nana misses him a bit. She's been whining a little and wanting some extra playtime.
I got a message from Woodley's owner, as well. He says Woodley is much better behaved since he got back, so apparently my little bit of training did some good.
Yeah, they got along: