How hard is it to train a large dog to get along with a small dog and not accidentally hurt it during play? I want to eventually get a papillon (probably from a breeder) and a large dog (probably a retriever mix from a shelter or rescue). I thought I'd get one dog, then get the second dog a few years later when the first dog is settled. Would you get the small dog first or the big dog? I was thinking if I got the small dog first, I could let it meet shelter dogs I was interested in to gauge their reaction . . . Then again, if I got the big dog first, I could do all the basic obedience training like sit and leave it before getting the small dog.