pulling on dog walks

Question
We have had a 7 year old australian shepherd for 6 years now after adopting her from a rescue. We have never been able to train her out of pulling on the leash while taking a walk, so we only let her just run in the backyard now but she is not exercising enough and is too heavy.  The trainer we hired when we first got her wanted us to use treats as we walked and to not walk forward unless she wasn't pulling, but we couldn't even get a block down the street and it required the patience of a saint to keep up this routine for weeks with no results.  Should we hire a dog walker to train her to properly walk on a leash?  Or do you have another suggestion because I would love to walk her and plan on getting another dog which we would plan on walking.  Once in awhile I try taking her out and am reminded of how difficult she is, including choking herself the whole time by pulling.  In addition she focuses on bikes or cars or anything with wheels and wants to chase them! Thanks for your advice.

Answer
At 7 years, this could be very tough to solve.  A dog walker might be able to train her to walk for him, but you would still need to train her to walk nicely for you.  

Maybe your best chance is a head collar. The leading brands are Promise, Haltie, and Gentle Leader. They have a strap going around the dogs nose looking something like a muzzle. They work by pulling the dogs head around. No other way gives you such great control with so little force. The prong collar is now a dangerous relic of value only for its macho looks. Do not consider using one without hands on instruction from somebody with plenty of experience with them.

Even with one of them, the dog may still pull.  If it does, gentlydrag her backwards until she slacks the leash.  You have to remember, training a dog to walk on leash is about training the dog, not getting somewhere.