Long check cords are great for teaching dogs to stay within a certain range, but I'm not sure how well an older dog would respond. It's easier with pups because you're teaching them a habit without them really even knowing it yet. Another option could be this... take your dog for walks as if you were hunting, not in parks and whatnot but in actual fields similar to where you'd hunt... when the dog starts getting too far away or you can tell it's not paying attention to your location, switch and walk the opposite direction, or hide behind a tree, or in a ditch, etc. Most dogs that have a connection with the owner will somewhat panic when they realize they're "lost." Obviously let the dog find you without too much trouble. Just get the point across. They remember not liking that feeling and will usually learn to keep better tabs on your position.