Everything I am going to say here is merely my opinion, some trainers will agree, some disagree. Both my girls were pullers. We tried and tried to teach them to talk with no assitance (regular collar). We tried a nylon slip collar (similar to choke, but safer. We used food, toys etc. no luck. With sadie we then tried a Halti. Wored great! She immeditaly improved, and does well without it now. When we need to remind, we put it back on and she remebers what heel means, although she sometimes tries to rub her nose on the back of your legs to get it off her nose.
Cincy was another story. We tried the Halti...she chewd through it while walking. we tried a gentle leder...she could pull it off her nose. We tried a harnees, but if you want a dog to pull, youget a harness...this only encouraged teh behavior. Finally we tried a Prong collar and what a differnce. many people think these are cruel, but truley, if used properlly they are not. They are actually safer then a other collars, because rather thent he constant pressure on the treachea, which can do long term damage, they give a pinch to the skin, more of a short term, surface level feeling. Try putting one around your upper arm and pull on it...it really doesn't hurt, it is just uncomfortable.

Both are girls walk well now. We still have our trianing tools and use them in high distraction situations, but the rest of the time we use the nylon slip collars (Premier).

Good luck! Teaching a dog to walk properally is a time comsuming, patience requireing thing. It took us almost a year with Ciny! Once you ge there it is great!!!