Get the temps up to 325 or so with charcoal and a little wood of your choice. Season up the prime rib to your taste. I prefer just salt, pepper and a little garlic powder. Montreal steak seasoning is another good choice, but I would add some salt.
I would turn it ever 45 minutes. Should be done in 2 or 3 hours or when internal hits 125-140 depending on how well done you want it. Let it rest for 15 minutes then slice and serve.
A meat like Prime Rib does not need low and slow. For that matter, I am finding that brisket doesn't either.