The pulled turkey filling for these sandwiches freezes very well. Try doubling the recipe and freezing any leftovers. Before serving, simply thaw the filling in the refrigerator and reheat in the microwave.
Heat the oil in a Dutch oven or large skillet over medium-high heat. Add the onions and celery; cook and stir until tender, 5 minutes.
Stir in the turkey, tomato sauce, ketchup, brown sugar, cider vinegar, Worcestershire sauce, mustard, chile powder, and salt. Cover and simmer until the turkey is fork-tender and the mixture is heated through, 45 minutes to 1 hour.
Remove the turkey from the sauce; coarsely shred with two forks. Serve the turkey on buns with sauce.