Okay, I asked Jane about this tonight. (Jane is this trainer: http://www.canissapiens.com/aboutus.html
When I described the articles that Moe 'guards', she wasn't surprised at all, and said 'I've known a number of Beagles who guarded tissues, and several who guarded space, like a spot on the couch.' 'What, like Sheldon Cooper?' I said, and she said 'Yes, if Sheldon Cooper bit people.'
I related the incident of the lens cleaner cloth and she feels it was too much too fast. In no particular order:
1. Do set-up exercises for quite a while, don't actually try to remove something he has until you have gotten the behavior you want established. If Henry is around, include him in the exercises, but since you will be throwing food for Moe quite a bit, you might want to not include Henry.
2. Take two items, one of which Moe likes more than the other. (Me: 'Haha, like a lens cleaner cloth?' Jane: 'Yes, or maybe some tissues!') Give the lesser item to Moe and then, a few minutes later, take the greater item and toss it five feet or so from him. He will leave the lesser object to get the greater object. Don't do anything. Let him return to the lesser object and it's still there, he can still have it. Do this a bunch of times, I mean a BUNCH of times. You are teaching him that you give him really good stuff and it costs him absolutely nothing. You never take away anything. It's good, better and even better!
3. Never physically restrain Moe in this exercise. Her comment on your move in trying to get to the den ahead of him was 'yeah, they are eight times faster than we are, that never works' and on hearing that he bit after the leash grab, 'he took that as a direct challenge and he wasn't wrong, it was.'
4. Once you have this behavior established, he will be less frantic about returning to the original item he was guarding, after you have given him better stuff. Then, when necessasry, you can unobtrusively establish claim to the item you want to remove. Jane gave this example: 'So I've done this exercise and he's confident now that he gets really good stuff from me. One day we're out walking and he gloms onto something disgusting. I toss a bunch of really good treats about five feet away from him, in a semicircle, and as he goes to get them, I move to the disgusting thing and put my foot on it. And in all the years I've done this, I have never gotten bit by the dog in the foot that is covering the object. Never. It's like I've established my ownership of it and they understand that -- but if I were to challenge them for it? It would be all-out war.'
Interesting, hope that helps a bit! I mentioned the muzzle and she shrugged and said what you already pointed out: it doesn't address the real issue. Moe is a guarder and may remain one, but management can prevent the more unpleasant consequences of that behavior.