When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 200F and preheat, lid closed, for 10 to 15 minutes.
Rinse the chickens, inside and out, under cold running water. Pat dry. Place on a rimmed baking sheet. Rub the outside of the birds with vegetable oil and season with salt and pepper.
Arrange the chickens directly on the grill grate and smoke for 2-1/2 hours, or until the internal temperature in the thickest part of a thigh reads 150F on an instant-read meat thermometer.
Transfer the smoked chickens to a clean baking sheet and let cool. Cut the chickens into 20 pieces - 4 drumsticks, 4 thighs, 4 wings, and 8 breast quarters (remove the 4 breast halves, then cut each in half). Divide the chicken between two sturdy resealable plastic bags.
Meanwhile, in a large mixing bowl, whisk the buttermilk with the hot sauce and brown sugar until the sugar crystals dissolve. Pour half into each bag of chicken. Seal, then refrigerate for 1 hour.
In a separate bowl, whisk the flour, garlic powder, onion powder, poultry seasoning, and 2 tablespoons each of kosher salt (use only 1 tablespoon if substituting table salt) and Black Pepper, freshly ground. Set aside.
On the stovetop, heat 2 inches of peanut or grapeseed oil (a true fried chicken connoisseur would use melted lard!) over medium-high heat to 375F in a Dutch oven, deep cast iron skillet, or heavy saucepan.
Drain the chicken pieces. Dredge a few at a time in the flour mixture. Fry the chicken in batches (do not crowd the pan), turning as needed with tongs, until it is golden brown - about 6 minutes for the breast pieces and 8 minutes for the thighs, wings, and drumsticks. Drain on paper towels before serving.