To cook en papillote (on the grill, enclosed in foil), preheat grill to medium-high heat.
Rinse beef to remove any unwanted smells, pat dry with paper toweling and season with garlic powder and salt and pepper, and set aside briefly. Make an oven pouch out of a 3 foot length of heavy duty foil by bringing the 2 ends to the center, folding the sides to seal, and leaving an opening at the top center through which to place the sauce and beef. Shake flour in the pouch to coat the inside. Sear all sides of beef on the grill, then put beef in pouch and pour 1/2 cup of the barbecue sauce and 1 tablespoon of the hot sauce over the meat (reserving the rest of the barbeque sauce and hot sauce). Seal the foil pouch by folding shut. Grill bagged beef directly on grill for about 30 minutes per pound. Ideally this should be cooked until fork tender, so that you can pull it apart with a fork.
Let beef rest 10 minutes before carving into thin slices, or pulling it apart with a fork. Heat the reserved barbeque sauce and hot sauce in a small saucepan. Then chop or shred the sliced beef and serve on Kaiser rolls or crusty Italian rolls. Spoon a bit of the extra sauce over the meat.