
I always have collars on my puppies from the day they arrive home(LOL I keep the small ones for reuse)I use rolled leather ones I was given many years ago. This way the puppy gets used to waring a collar & quickly ignores it. I then(only under supervision)leave avery short light lead attached so they get used to having something attached to the collar, however I ever teach heelwork on lead. With titbits & toys I do a couple of minutes several times a day getting my puppies to walk with me off lead, it doesn't have to be really close at first just as long as they follow me, I then work on getting the puppy in a normal heelwork position by luring in using very tasty titbits again only for a couple of minutes.
By the time they are ready to meet the outside world I usually have them walking normally off lead, I then attach a very light lead & do some lead training at the dog club. I've never had a problem getting a puppy to walk on a lead & because I train off lead they never learn how to pull
You could try reverse walking take the puppy a little way down your drive or path & have someone call him back into the house & then treat & loads of praise. Gradually increase the distance & hopefully the puppy will enjoy it & walk both ways It worked for a friend of mine who had a very very stubborn Dandie Dinmont who at six monhs old was still not walking on the lead