Cut pork into 4-by-4 chunks, cutting away as much fat as possible. Mix together salt, pepper and garlic powder. Rub mixture on all sides of pork.
In a deep Dutch oven, add oil and heat on medium-high and when oil begins to smoke, add pork. Sear on all sides in batches.
Reduce heat to simmer and add all pork back to pot. Cover and cook for 1 hour, turning meat every 15 to 20 minutes.
After 1 hour, add milk, re-cover and continue to cook for 30-45 minutes. Remove meat to drain on paper towels.
While still hot, using 2 forks, shred pork, and if needed re-season with more salt, garlic or pepper. A squeeze of fresh orange juice finishes the dish. Serve with flour or corn tortillas.