I'd recommend good training classes. Our last cocker pulled like hell, and I thought I was following all the advice. The training class for our new cocker is like a revelation. There are things that they can show you that just translate in books. I had been stopping as soon as he pulled, going home etc. But now it is amazing. They pointed out that a dog can't walk to heel until he knows where heel is. Then they said to only start introducing the command when the position is clear. We have to walk the dog in a circle around us, with a treat and call him to our side, and as soon as the dog is in the right position give the treat immediately. (I used a clicker at home). Then we introduced saying heel at the same time, as soon as the position was right. Now when he starts to get slightly ahead (rarely), I may do the circle, or I just walk backward excitedly and he comes to me, then I do a small circle and get him back in postion. This only took two weeks to get consistent, whereas the stop start method never really sunk in. Now I just tap my side and he comes in to heel. See what I mean, you can't write it down, it needs to be explained. I would say you need to do it one dog at a time, and with some really yummy treats.