I'm going to tell you about my experience as well. Uni is a super puller. She doesn't sniff too much, she just loves to run. She's got crazy energy and if she gets overly anxious she will get a foamy/drooly mouth too.
I have tried the harnesses Brit recommended. It works for 99% of dogs, but did not work for Uni. I guess she is exceptional
She would just keep pulling to where the lead would go up under one of her armpits and continue to pull with three legs.
For the stop and sit method... She will sit next to me but bark, and I mean LOUD and keep barking barking barking while sitting. It's like she's saying "I'M SITTING ALREADY LET'S GO LET'S GO LET'S GO!!!!!" But I did not want her to sit for a second and bark her head off and keep going. That would tell her that barking loudly will get her her way. And I seriously stood in one spot for about 5 mins and she was still barking.
I tried the stop and change direction method.... Uni does not care what direction we are going in, as long as we are moving. So didn't work.
The only thing that I have found that works for me is the retractable lead. And that is the ONE thing you are absolutely NOT to get if you have a puller (rewards them with what they want--getting farther away, with the problem you want to stop--pulling). I got the extra long one 23'. When she is on this lead, she doesn't think she is on anything. She will run out far, and when she thinks she is too far, will run back to me. Same as when she is completely off leash.
I think you should thoroughly try all the methods mentioned here first, before you consider a retractable. i believe Uni is a special case and I am good with training her, that is why i left this as a last resort, and for some reason it worked for us.