If you have time, toss wings in salt, pepper and buttermilk, and let sit refrigerated for an hour and up to a day ahead.
Heat a grill of your choice to about 300 (medium) with indirect heat, and cook wings indirectly for about 15 minutes, until "blonde" - no char or caramelization necessary at this point.
While wings are cooking, combine the fish sauce, brown sugar, oil, Boat Sauce and pepper in a shallow bowl.
Move the wings over the coals directly and raise heat to about 350. Cook for about 3 minutes on both sides. They should be getting some color at this point.
Remove wings to bowl and give a good toss. Return them to the grill and cook them again for 2 minutes per side, basting before and after each turn and staying vigilant that they don't singe. If they are not dark and lacquered (without being burned) after 2 minutes per side, keep basting and turning until they are.