I might add, if your going to go a medium rare and you have a few folks who like their prime rib a little more done. One recommendation would be to take their slice and finish it in the warm au jus. It doesn't take long and keeps things moist.
One Briquette that I use occasionally that reminds of the Weber bricks are the Jealous Devil Briquettes. Not quite the same but similar.
Using them today for a long smoke in the WSM.
Never had the CI grates on this older Weber Genesis I currently have. Had the older porcelain enameled grates and currently have a custom set of thick SS grates.
Let us know how those work for ya.
You can also dry brine them for a bit before you add anything else to them.
Little kosher salt on the skin and let set in the fridge on a cooling rack and pan for an hour or so before you cook em.
If you add any bbq rub or seasoning to them just remember you pre salted them.
Helps alot