I coat the prime rib with a mixture of Turbinado Sugar, Kosher Salt, Smoked Paprika, Cracked Black Pepper, and a slight dose of cayenne pepper
I put the prime rib in the smoker at 250 degrees and cook it to 135 degrees internal. It takes approx 20 minutes per pound to cook it in this fashion.
If I am cooking a single roast I wrap it in foil, if I am cooking large amounts I drop the roasts in a clean ice chest to rest for 10 minutes or so.
If I am cooking large amounts I cut whole primes into thirds----because there is many people that request "end pieces"