I have 3 and I'm always trying to find creative ways of just using 1 leash to walk all of them. I bought those handles that has a D ring and you just attached the leashes to it. Then I use a coupler for Naboo and Wookie and attached Squeekie's leash in the handle. Anyway it'll probably make more sense if I attached a picture of what I'm talking about.
I think the only way to stop the pulling and dragging is training them to walk correctly in the first place. As for my 3, my Naboo is the biggest at 15 lbs, then Wookie at 9 lbs, then Squeekie at 6lbs. I put Naboo and Wookie on the coupler and Naboo would drag Wookie with her. When she does this I would correct her by pulling her back and shortening the leash to right next to my leg. Or I would stop entirely and she would stop as well, look at me, and I would tell her to come here and point next to my leg. She hesitates and takes her time, but I won't move until she comes. (While people are passing by and probably think I'm a nutso
).
We keep doing this over and over again until "she gets it" (we walk 1 mile), then when we turn around to go home, all three of them are in the same pace as I am. All 3 of them are walking right next to my leg and no one is getting dragged.
And of course, when we go out walking the next day, they completely forget and I have to teach it to them again.
And I just want to add that Squeekie is completely trained to walk without a leash, but I leash her anyway for safety. I did this by always calling out her name when she gets about 3 ft away from me (then she would run back to me wagging and all, almost like apologizing she wandered too far
). When she doesn't listen I would leash her back up and when she's good, I unleash her and do it over and over again.