There are a few points in the post that I 'have an opinion' on....
2. When the dogs greet and sniff each other, talk to them in a happy, friendly tone of voice and offer each one treats (give the treat to the resident dog first).
I'm not for letting strange dogs sniff, even on leash. Cleo enjoyed sneak attacks when sniffing. I think the neutral walk is a better way to get the dogs a little used to each other before this step.
I also never involve treats of any kind, especially right off. Most dogs will not go after another dog in teh presence of a treat, but some do.
3. Introduce the dogs only for brief amounts of time, but do it repeatedly.
This is very good, but I would add that outside of the introductions you allow them limited access to get used to each other. Maybe through a baby gate or under a door.
4. If one dog acts submissive to the other (rolls over and shows belly) that’s great - reinforce this behavior (say “good boy/girl” and give treats) even if it is the resident dog.
6. Watch for dominant body postures (one dog putting his chin or neck on the shoulders of the other dog, or placing a front foot over the others shoulders or back). If the other dog submits to these postures that’s fine, if not, interrupt them by calling them away from each other and having them sit.
Both of these could lead to serious arguements down the road (even if it's a short road). Do not allow eaither dog to diminate the other, especially at the beginning. Once you
have established the pack order, you can allow your 'chosen one' to dominate, but until then the one that is being submissinve may decide that it has had enough and challenge that order. That can manifest in overt aggressive behaviour or passive aggressive behavior such as peeing on the other dog's bed or taking food and toys consistantly.
Some dogs don't give physical signs of tension, so you need to know your dog. Connor wags his tail happily before he gets aggressive. A confident dog is sure of his abilities, so he has no tension/nervousness.
8. DO NOT hold one dog while the other is loose.
10. Until the dogs are comfortable with each other, do not let them alone unsupervised while you go get a drink or whatever.
12. GO SLOWLY - if they do not do well at first, separate them except during managed interactions. Make sure all interactions are positive using happy voices and treats.
Excellent. But neither dog should be loose at the beginning stages. And see my thoughs about treats above.