I walk all three of mine at once. When I just had Sylvia and Harley I bought a splitter, sometimes called a coupler. Then when I got Morty I added another one. Three dogs, one leash. It's nice because they don't get tangled. This works best if the dogs walk well on a leash already and are around the same size. Sylvia is 19lbs, Harley is 22lbs, and Morty is 16lbs and it works great.

I'll snap a picture of our set up if it will help.