In a large pot, add the first 6 ingredients to 2½ gallons of water and bring to a simmer. Remove from heat and allow to cool; refrigerate until completely chilled.
Brine the ducks in 3 brining bags for 8 hours in the refrigerator.
Preheat oven to 350 degrees.
Remove the ducks from the brine, rinse inside and out, and pat dry with paper towels. Discard the brine.
Fill cavity of each duck with Dressing (don’t pack it too tightly; extra dressing can be baked in a pan alongside the ducks).
Tie the legs of the ducks together with butcher’s twine and roast, breast side up, on a rack in a roasting pan until an internal thermometer inserted in the thickest portion of the thigh reads 180 degrees, about 1 hour (more for larger birds).
Remove from oven and let rest for 10 minutes before carving.