I usually get pups used to leashes by having a long one and just letting them follow me around the house and yard, using the leash to stop running off or heading in wrong direction only. For a pup that is already having issues--take him to an unfamiliar place and have him follow you--he will want to stay close for safety, and will have no house to try and retreat to. At home, you could try gradually carrying him farther and farther away from home--each time putting him down and having him walk home on the leash--the leash is enabling him to get where he thinks he wants to be. Start close at first so he recognizes where home is.
I always have an older dog to help with training--they will follow a dog they know ANYWHERE.