Trim excessive fat from prime rib and do not remove all of
it, leave at least ¼ to ½ inch layer of fat. As the fat melts it bastes the
meat and keeps it moist and tender. If your prime rib came with a cap, dispose
of it. The night before barbequing, sprinkle the roast with the rubs and
seasonings over the entire meat with your fingers. Cover and let stand in
refrigerator overnight.
When ready to barbeque, prepare grill as to allow enough
charcoal to slow cook roast for approximately 3 to 4 hours depending on grilling
temperature in barbeque, size of roast, and doneness. Ideal slow cooking is
about 200 degrees. Form the heat zones by raking the coals into 2 piles at
opposite sides of the grill, place a drip pan in the center below the barbeque
grill as this will help minimize flare ups. You will also need to add 12 fresh
coals to the sides every hour.
To complete the preparation of the roast for cooking. Add the
mustard to the exterior of the roast with your hands and smooth it out like
frosting a cake. Then sprinkle rock salt to the exterior of the meat over the
mustard while padding it in to about a ½ inch layer.
Place roast in barbeque – fat side up. Place a barbeque
thermometer in end of the roast leaving it sticking out ½ inch from touching
the roast. Cover thermometer so the barbeque smoke does not fog it up. Tip: take
an empty coke can or beer can and cut the bottom off about 2 inches up and
insert the bottom end of the can over the thermometer. This will protect it from
the smoke and allow you to remove it to check the temperature for doneness. You
can use an instant read thermometer to check the roast.