After a month of daily clicker training, Major now walks much better on his lead and is more responsive to commands.
While out walking (at this point in time) I keep him on two forms of restraint: a halti lead for close heeling, and his harness when walking on a longer a lead.
I attach a clicker to my belt, close to the pouch containing food rewards. In this way I can give a command, click and reward in very close succession. It's a process that's working well for me and my dog.
For food rewards, I use Goodos, with each Goodo cut into about six pieces. I give lots of food rewards, but each piece is tiny -- and tasty.