Harnesses will actually promote pulling in some cases. Hence why sled dogs wear harnesses. Showing dominance over the dog isn't going to automatically promote or train a dog to walk on a leash. Alpha rolls can create major problems if you don't know what you're doing; the dominance advice above is not good advice if you are not experienced in training. There are so many adverse affects tat can be caused by the dominance training, that it's not advised for the majority of pet owners to attempt. Dominance training can cause more behavioral problems if the trainer or owner does not use the techniques properly.
Walk with a 6 foot leash, never using a retractable leash. Use a regular flat buckle collar.
Walk the dog with a slack leash, as soon as the dog starts to pull, stop as soon as the leash is taught. Call the dog's name so that he turns his head to look at you, which will cause the leash to slack, praise, and start walking. It's a long process, and you'll want to start with no distractions, and slowly build up distractions. IE don't go to the dog park or pet store to start training the dog. Start in a hall in the house and move to the yard, street, etc. As long as the dog is walking with even a slight slack in the leash, praise him and keep going, as soon as there is no slack, get his attention somehow so that there is just a slight slack in the leash. Use treats or just verbal praise.
When the dog is leash trained, you can work on heel so that he walks next to you.
The goal is to walk, so the reward is being able to walk. If you stop walking, the dog isn't reaching his goal, so he's going to find a way to walk. If you stop moving, he'll find another means to get where he's going.
Bulldogs are very intelligent dogs but they can be very stubborn. They are not for people who do not have proper experience training. You will need to be consistent at ALL times.