I used the Easy Walk harness back when Jackson was a pup and we loved it. He started walking perfectly within a few days. We used the harness for a few months and then "graduated" to a regular harness.
They have some front clip harnesses now that has BOTH (d-ring on the back and the front) so it's easy to switch. Also, the Premier Quick Fit harness has both but it's not really targeted as a training harness like the Easy Walk.
Here are some:
See Spot Shine: Front-Clip Harnesses: Updated Reviews