Thanks Demo for correcting me. I've not used either, so I just did a google search and linked to what I thought was it. It was more so I could be a smartass in my replies
One method I've used, and although I'm probably going to look like the 'bad guy' with always making these types of suggestions, but they are alternatives to what is offered. I have used some of the methods here as well (not just on this topic) but I have other 'alternatives' that I've used with success.
I have trained the heel with a very short traffic lead. What I so is basically measure out the parameters for me to hold the lead, and if the dog forges, they would basically put themselves into a hanging choke. It takes a little thought and strength to get it all working properly, but once it is set to go, the dog usually picks up quickly. You hold the lead, and they are in a perfect heel, but if they forge ahead without you, so long as you are holding the lead properly, the dog will put themselves into a choke, and then it becomes a decision of "choke myself or move back to the spot that didn't choke me".
Most dogs will comply quickly.
If anyone needs clarification/elaboration, please let me know.