A slip lead should not be under the chin. It should rest slack on the lowest part of the neck by the shoulders. IMO it is not suitable for very young puppies that have soft bones and may fight the restriction to the point they damage themselves.
Have your pup wear a collar in the house but not when you can't supervise. This gets them used to weight round the neck. They niggle at first but soon realise that the collar is just part of life.
Harnesses used correctly don't teach dogs to pull, but I seldom see them used correctly and they rarely if ever come with instructions. The harness should have a chest attachment for the lead, and another behind the neck by the shouider. A double-ended lead or two separate leads should be used: one on the chest ring, one on the neck ring. Lead the dog off the neck ring, but when it tries to pull, the chest ring comes into action and turns the dog towards you. This isn't where it wants to be, so they teach themselves not to pull. All the handler has to do is stand still when the lead is tight and move on the instant it slackens. This has to be repeated over and over to begin with, but if the human is consistent, the dog learns very quickly. The dog makes the choices and the reward is walking forward.
Holding the lead - sorry can't post pics and I do appreciate many people are visual rather than verbal, but I'll try again.
Fasten dog end of lead to something like a chair. Stand beside the chair (whatever) as if you are taking it for a walk. Have your arm nearest the chair down by your side. Your little finger points rearward to you and your thumb points forward. Rotate your hand so that your thumb lies against your thigh and your little finger points outward away from you towards the chair and your palm is facing behind you. With your hand in that position, lift your palm by bending your elbow, then lower your palm until it is touching the lead. The lead should pass right across through your palm with the chair at the little finger end. Now you should have the lead held correctly. Let me know if this works for you, and if not I'll try again.
Have your pup wear a collar in the house but not when you can't supervise. This gets them used to weight round the neck. They niggle at first but soon realise that the collar is just part of life.
Harnesses used correctly don't teach dogs to pull, but I seldom see them used correctly and they rarely if ever come with instructions. The harness should have a chest attachment for the lead, and another behind the neck by the shouider. A double-ended lead or two separate leads should be used: one on the chest ring, one on the neck ring. Lead the dog off the neck ring, but when it tries to pull, the chest ring comes into action and turns the dog towards you. This isn't where it wants to be, so they teach themselves not to pull. All the handler has to do is stand still when the lead is tight and move on the instant it slackens. This has to be repeated over and over to begin with, but if the human is consistent, the dog learns very quickly. The dog makes the choices and the reward is walking forward.
Holding the lead - sorry can't post pics and I do appreciate many people are visual rather than verbal, but I'll try again.
Fasten dog end of lead to something like a chair. Stand beside the chair (whatever) as if you are taking it for a walk. Have your arm nearest the chair down by your side. Your little finger points rearward to you and your thumb points forward. Rotate your hand so that your thumb lies against your thigh and your little finger points outward away from you towards the chair and your palm is facing behind you. With your hand in that position, lift your palm by bending your elbow, then lower your palm until it is touching the lead. The lead should pass right across through your palm with the chair at the little finger end. Now you should have the lead held correctly. Let me know if this works for you, and if not I'll try again.