As we are teaching both of our dogs these rules, we currently do not permit them on the furniture, we avoid situations we know could trigger aggression, both dogs are in separate rooms behind baby gates when we are not home, they sleep in their own crates at night, they get fed in separate rooms, and they are not allowed in the front room when the mailman comes. Play is always supervised and toys are only permitted when the other dog is not around. Hazel and Béla each have several short training sessions every day where they learn to stay on a blanket/bed and relax. On walks, they have learned to automatically look at us when they see another dog, cat or stranger, and they get a treat in return. Otherwise, as long a nobody is growling or snapping, they can do as they please.
Dog training is a work in progress and we know it will need to continue for the remainder of our dogs' lives if we want them to get along, so we can all enjoy each others company.
Check out Dr. Patricia McConnells's book "Feeling Outnumbered?" on managing a multi-dog household which we sell at the clinic and also some of the links to the articles below.
Wishing you and your loved ones, a very merry holiday season and a Happy New Year (Let's make it a good one!),