Please use a harness and collar combination with newly adopted or skittish dogs. It is surprising how many rescues don't require more than a flat collar when sending a dog into a new home. So many dogs go missing in the city as they are transported from other countries and rural areas.
Most have no idea how to walk on a leash and a collar much less in congested environments like Seattle. A flat collar should only be used with dogs who walk without tension, are confident with their handler and experienced in many environments.
Like prong collars, they can damage the neck when they pull. Some harnesses are better and more effective than others. Please work with a positive trainer if you want to save time, energy and to help your dog acclimate quicker to their new environment.