I have worked with feral dogs in rescue who had never been on a leash, adults. Teaching loose leash walking isn't hard, but you need to back it with the "leave it" command. Mary's site is so simply it will make you feel faint. And it works. No pop and jerk, just good positive training. The lessons are on the left, other issues on the right.
I certainly would go through most the training, then get into an obedience class, but make sure by positive trainers .. go watch a couple of sessions first.