I just bought a leash coupler for my dogs to avoid disaster with tangling my feet when casually walking. We went to a training class today and I think it's going to be a great help with training, too. Since Luca, who is 16 months old has already learned some commands, at least theoretically, I give he command to him first, e.g. "Go to your bed". Calla, who is 6 months, has to follow along since they are coupled and so she learns the command by demonstration so to speak. I think it will help her learn quickly.
We use a coupler also...I don't know if it helps with the training...but the "warning siren", tested the first Tuesday of every month, went off and I am here to say, they RAN...perfectly side by side...dragging DH behind them....
I used coupler with Samantha & Mickey. So much more preferred than tripping over them. I did have a couple problems with one of them always trying to be in front of the other which left me behind and each of them wanting to walk next to me. Truthfully, I did not work very hard on correcting this since Mickey wasn't staying with us permanently but I do plan on using it for Samantha and Charli. A little too early yet since she is so much smaller than Samantha. I am definitely going to work with Debbie Kaikaka, our trainer (member of DK) on this!