I personally have never had any major problems with introducing dogs. Lots of people here have used the two week shut down period with success--I have never had to. Its going to depend on the dog...is the new dog aggressive?shy?scared? I have noticed that with all the bigger dogs I have had there was no problems...the smaller dogs seemed to think they were pit bulls and most of them spent a day or so in the crate observing their surroundings...only one continued to give me a problem-a poodle...he didn't like other dogs, hardly tolerated them and even in his new home he is the same way. This is going to really depend on all dogs involved!
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD