In a large bowl, add the salt, water and cider vinegar, stirring thoroughly until most all of the salt is dissolved. When the salt is completely, or mostly dissolved, add the brown sugar, bay leaves (don't crush the bay leaves), garlic and 1/2 cup of the dry rub mix (we'll use the rest later). Stir well to combine.
Place the pork roast in a 1 gallon freezer bags. Pour the brine solution into the bag until the shoulder is completely covered. Close the bags and place in the refrigerator for at least 8 hours and up to 24 (preferred).
Remove the pork roasts from brine solution, pat dry with paper towels, place in several large roasting pans, leaving 1 inch clearance on all sides of the roast to accommodate the cooking juices which will accumulate. Press the dry rub onto the surface of the roasts, pressing it so it will adhere to the surface. Generously coat all sides and under any flaps with the rub.
When done make sure the fat layer on the pork roasts is on the TOP. Insert a digital probe thermometer into the thickest part of one of the shoulders, but not touching the bone. Place the roasting pans, uncovered, in the 225 F degree oven on the middle rack if possible.
Monitor the temperature throughout cooking. Do not remove roasts from the oven until the center of the pork roasts reaches 200 F degrees. The internal temperature should reach at least 200 F degrees to get that tender, falling apart shredded meat. Don’t worry about the long cooking time. They will still be juicy and flavorful because of the brining. Cooking at 225 F degrees, your shoulders will take between 1.5 to 2 hours per pound to cook. An 8 lb. pork roast will take about 13 hours.
When the pork roasts' internal temperature reaches 200 F degrees, turn off the oven, leaving the roasts in the oven and the thermometer in the roast. Your pan should have plenty of wonderful cooking juices in the bottom. If not, add 1 cup of water and cover the pan to retain the moisture while your roast is resting.
Let the roasts cool (for approximately 2 hours) to an internal temperature of 170 F degrees before removing from the oven.
When the temperature drops to 170 degrees, remove the roasts from the oven. Place the roasts on a large, clean work surface and remove any remaining fat from the top. Pour the juices from the roasting pans into a fat separator cup to strain and reserve the juices.
Shred the roasts with two forks, it will pull apart very easily. Discard the bone. Add back in some of the defatted pan juices. IT’S VERY IMPORTANT to taste and sprinkle with kosher salt as you go.
If frozen, thaw pork and juice over night in refrigerator. Then re-warm in a 350 degree oven for about 15 -30 minutes. Add in reserved pan juices as necessary to achieve desired level of moisture.