Carve the roast into something like a long, 3 dimensional, rectangular shape. Make sure the shape is relatively even so that the rotisserie motor will not strain when rotating on the up-turns.
Fire up a rotisserie with charcoal as the heat source. (Low heat for this dish is crucial. One layer of coals, scattered on the bottom of the pan, should suffice.)
Push the spit through roast, length-wise. Attach it to the spit with the provided skewers. Dry off the roast with paper towels, and salt it down. Sprinkle the chile powder over the surface of the meat. Coat the flesh and fat thoroughly. Position the spit on the rotisserie. Turn the motor on, allowing the roast to spin. After 2 hours into the cooking time, add a layer of pre-ashed charcoal to the bottom of the pan. Inspect the roast for doneness at 3 hours. If the roast is shrunken, somewhat blackened and hot to the touch, it is finished. The roast will require 3-4 hours to become pullable.
Remove the spit from the rotisserie, and allow the meat to rest, tented under aluminium foil for 15 minutes. Chop the cilantro coarsely. Break or shred the meat apart. Taste the roast for salt. Dust the strands of meat with more chile powder. Sprinkle the meat with cilantro and spritzes of white vinegar. Serve with fiery-hot, jalapeno salsa. The pulled meat is an excellent choice as filling for tacos or burritos.