I have the same problem with Paddy and Gladis, I tried every time the dog pulls stop wait for the leash to go slack before starting again. It was very hard with both of them together. next a harness worked for a while with Paddy, I had to put Gladis back on a normal coller she still pulled her skin was sore where the harness was. I have found now that when I take them both out on normal collers when one starts to pull give a little tug on the lead and say nicely. If they still pull say "I'll fall" like I mean it. We are getting there. I can not walk them on their own it would take too long. :)