I would NOT recommend physical corrections for resource guarding (or anything IMHO). He's guarding because he thinks you're a threat. If you put him on his side, scruff shake, etc., you just confirmed you are a threat. Feed him all of his food by hand for a while, maybe a week, and that will probably take care of it. Once you go to him eating on his own again, start with the lower value things that he's not guarding, walk by while he's eating and toss a high value food item to him (like the chicken). You do that for a few days, now you give him his high value items and walk by and toss more food to him. You are teaching him that you coming near means more good things, not the loss of good things.
Work on teaching leave it and drop it. He's got no reason to guard if he's willingly dropping food on command. Check out kikopup's videos on youtube for instruction. I can give my dog a whole chicken, tell him to drop it after he's started eating, and he will, and that was 100% without touching him or intimidating him.
For many dogs, physical corrections can work, but for some, they can create much worse problems and that risk doesn't merit their use, again, IMHO. You correct a growl, so the dog stops growling but still feels threatened, so now he goes straight to biting without warning. Corrections aren't going to change the state of mind, they're going to suppress the behaviors.