I don't pretend to be an expert, and I am only talking of one past experience so take it for what it's worth! I had Buddy and Tasha when I moved in with a girlfriend who had two cats. They essentially despised each other but we pretty much just let them figure it out for themselves and the odd part is.........they did. Don't get me wrong, we didn't lock them in a room to "sort it out", we kept a close watch on the happenings and the pups ended up with a scratched hooter now and then, but they figured it out. Thankfully, I'm done with the cats (actually I liked the cats, thankfully I'm done with her! lol). It seemed like the more we interfered and tried to effect progress, the slower it went, the more we let them figure it out themselves, within reason, the quicker it went.