Hey David,
I did use the correction Ed describes but for a different reason. I think he mentions that the cheek grab and immobilizing the pup works well when a young puppy gets really wound up and starts getting too wild with you.
It's more of a way to calm an out-of-control puppy down while re-asserting your dominance in a calm manner.
I try to mimic how a bitch would correct her pups if they tried to steal her food (or how any dog would correct a lower-ranking dog who approached while he was eating).
I feel that it should be a much more instantaneous and meaningful correction than grabbing and holding onto the pup's cheeks. You want the pup to back right off.
A growled "NO!" coupled with a quick grab & jerk on the scruff might work on a young pup (not shaking the pup, just a quick grab and release).
A pup's mother would growl, grab her pup's muzzle with her mouth and pin the pup to the ground (which usually results in the pup yelping).
If your pup blows off the quick scruff-grab, maybe a light pop with a puppy prong is in order.
When my pup was around 12 weeks old, I had trouble correcting her hard enough to prevent her from trying to attack my pet rabbits. She can be quite the knuckle-head at times and was pretty hard for a pup. I PMed Ed (Frawley) for advice and he recommended a puppy-prong.
Worked like magic and it hasn't affected her drive, enthusiasm or bond with me at all! Ever since the first 1-2 prong corrections, all I need to do now is say "No" in a firm voice when she's bugging the rabbits and she immediately leaves them alone. (Lots of praise for that!)
While it's a BAD idea to correct a puppy for obedience issues (as in ignoring your obedience commands), I do think it's fine to correct them for inappropriate pack behaviour. That would definitely include getting in your face while you're eating
How much of a correction would your pup need to back off and leave you alone when you're eating?
Only you can answer that. Use the lowest level of correction possible (don't go and traumatize your pup), but make sure it's effective. Some dogs back off with a verbal warning alone, some need a prong.
If your dog doesn't back off after 1, maybe 2 corrections, you're being too soft on him.
A short yelp out of the dog/pup is an acceptable response in this case, but a scream means you've overdone it.
I hope that helps! Just do what you feel is right for your dog, they're all different. My two oldest guys never required a physical correction to back off during my mealtime - they respected my rank enough that a verbal warning sufficed.
My crazy knuckle-head pup on the other hand required an occasional pop on the prong
Just be sure not to hold a grudge against the dog. The second he backs off, you should be pleasant and relaxed with him again.
Hopefully others will give you different options to choose from. This is just what worked for me. Good luck.