Create a pattern:  When you are offered food or a toy, avoid putting your teeth on skin. 
 

IF < THEN
IF you shift away from the food, THEN you will get food. 
IF you shift your weight toward the food, THEN you will not get food.

 

Rule number one:

Leave your fingers in the way whenever you deliver treats, so he expects to always have to go around them to get to the food.  We are teaching the dog how to automatically avoid putting his teeth on our skin whenever food is offered.  We will show him exactly what he should do to make the food he craves available.

 

Food should be presented directly into the dog’s mouth without him having to reach to get it.  If fingers are always in the way and the hand is steady, the dog will soon slow down and stop grabbing, as experience tells him he need only wait for the food to come to him, and lick around the fingers to extract the food from inside the hand.  Next, you will show him that if he pauses when the human says "wait" it will reliably make a release cue happen which makes the food instantly available.  Being gentle and patient works.

 

FEEDBACK: 

• If teeth touch skin yelp “OUCH!!” and calmly retract the offering.  Hold your closed fist against your chest.  Go still for a beat.  If the dog pauses, catch that tiny stillness with a "Yes!" and deliver a treat immediately to his mouth from the palm of your hand, like feeding a pony grain.

• When you can feel that the dog is trying to adjust his technique by showing any degree of self-restraint, and/or switches to using his lips and tongue, mark it with a "Yes!" and open your food hand and deliver the reward. "Good job!"

 

Rule number two:
Use soft treats, like tiny balls of cream cheese, cubes of meat or chopped hotdogs.  Choose a texture and hardness similar to skin. If the dog is bearing down with enough force to crush a hard Milkbone and misses, he will surely pierce your finger.  For particularly hard mouthed dogs, start with a lick-mat before offering the same on your fingers.  Praise the dog for licking whipped cream, cream cheese or peanut butter off your fingers before you move to higher value soft treats: cheese, wieners, meat.  Croon “careful!” or “eeeeeaasy!!” then hold the treat loosely and encourage the dog to fish it out with their tongue, not their teeth, to extract it from your hand.

 

Rule number three:  

Don’t hold the food too high!  Deliver the food to the dog at nose level or lower.  People who are afraid of getting snagged by teeth often dangle the food tentatively, just out of reach, which encourages leaping and grabbing. Frustrated dogs will snap at a moving target. Teach children in the family to deliver the food in a closed hand and feed the dog from a stationary open palm, like feeding a pony grain.

 

Rule number four:

Don't tease.  Don't compete.  Don't threaten, don't challenge.  No correction.  Be calm, be gentle and be kind. Your dog will slow down and think when he learns that it's easy to gain access to the reward.  Show the behavior, listen for the marker, the praise and food delivery will happen.  No doubt, no frustration.  Just calm, productive repetition.