I do drop in visits with kitties exclusively. Upon arrival at a client's home, I typically spend the first five minutes letting the resident cat get used to me, whether that's through letting them sniff me, giving then pets, playing with a mouse on a string or just sitting next to whatever piece of furniture they are hiding under and talking them through their separation anxiety. Then I quickly take care of chores, which can usually be finished up in a matter of minutes. The rest of my visit I spend paying attention to the kitty (or kitties) in whatever form they will accept.