When I deal with dogs afflicted with what other trainers term "resource guarding" (which in actuality is an instinctive "excuse" to vent held back energy, i.e. unresolved emotion) my method is to turn the object of friction, into an object of flow. I do this through Push-of-War. Whereas I've seen on the web some trainers wearing heavy gloves and letting the dog learn that biting is futile and then giving the dog food, and there is also the positive trade and switch out method so that the dog doesn't perceive scarcity, there's always more where that came from. Cesar does a clever move with blocking. But all of these approaches haven't precisely defined the problem and can therefore still be building on a foundation of load/overload. I feel the approach I'm advocating directly accesses the flow dynamic by (a) triggering the held back energy that (b) the dog then marshals to overcome resistance and in the process softens. The dog changes its perception of the object because its relationship with its owner shifts in the same breath. The dog perceives more flow in making contact with person (Pushing With) than in growling, snarling and lashing out (Pushing Against) over the food bowl, resting place, bone or toy.
Of course it's better to do this right from the beginning and imprint a puppy with flow rather than resistance creeping in and then letting instinct have its way. So when Hessian was young and in the middle of the training/channeling-of-resistance-into-flow regime, I gave him a whole chicken and asked him to push it to me. I wish I had taken a video. He pushed in with the same intensity with which he was about to crush it. After I released him he dove under a bush and ate it like a wild coyote, I swear his eyes turned yellow. Now Hessian is pushing 13 and has been a lazy farm dog for a number of years (my aim being to nurse as many days out of his frame as possible by a life of leisure). Today after giving him a marrow bone I asked him to push it to me to see where we were at. While I'm sorry about the camera work, I was happy to see how soft he still is.
Dogs want flow, that's what they fight for. In their dealings with man, they either learn to push with us, or learn to push against us. It's our choice. Keep On Pushin!