if your doing a roast (any) on the grill. Use a open pan, no fire/coals directly under pan(indirect method), completely coat(heavy) the roast in any, cheap brand of yellow mustard, really clop it on, cook until internal temp is what you want or is required. Mustard coat will be burnt and crusty, peel it off and discard. Meat will be tender and very juicy as the mustard coat sealed in all the juices