At your local dog park.

[thesummerqueen]

I think Min has the right of that one - eventually he's going to have to pee (unless you have a yard for him to go in).

We had success carrying around a bag of treats Shutter really really loved. He had a problem with heeling (or even walking around us at all) and pulled constantly. So we used the treats to keep him moving beside us and his attention on us. I've had to use them less and less to the point of him even automatically sitting down next to me when I stop at a crosswalk.

It's hard to pull a big dog into action, so the treats might prompt him to give up his howling and follow you around. You might try keeping the harness on him in the house too just so he gets used to wearing it. It's not worth punishing them at all for not listening - just like stubborn kids, they know what they want and they'll run roughshod on you unless you stay consistent and insistent.