Ok... no one's saying it doesn't work with certain dogs. No one is doubting that you've used it successfully. I'm glad you have. I've worked resource guarding with dogs and food too - professionally.
But I do entirely doubt that you could use it with my bitch when the mere presence of food amps her up around other dogs. I've said before that your timing does not matter. You can't "reward her before she amps up". Well, ok, you can - once. Then once food becomes a part of the picture she's now guarding you AND the food. That's it. It just doesn't matter how good you think your timing is. If she thinks there's a chance that food is in the picture, she's totally over aroused. Associating the approach of other dogs with food would make my dog go, "Other dogs are coming, time to guard my food!" It's nice if it doesn't work this way for the dog but sometimes it does. Whether or not you want to believe me isn't really my concern, I guess.