When all of my dogs were puppies I put my hand in their bowl every so often to get them used to me being around them with food...fed them from my hand...never dealt with the growling issue but I can say none of my dogs are food aggressive with people at all. They can be brats about sharing with other dogs though. I could take a steak out of their mouths and they would be okay with it. One thing I did that may help is a lot of times when I put my hand in their food dish I'd be adding a treat to their dish too. So me putting my hand in their food was often a positive thing for them. You may have said you already tried that I didn't read all of the responses so sorry if somebody mentioned that already.