I have been wanting to do the Campo Grande pork forever after seeing their ads and Al Frugoni cooking them on Instagram. If it were me, I wouldn't want to use any slathers or a lot of rubs that will mask the flavor of the pork. I would keep it simple with SPG and let it ride open until you get that nice dark red crimson color. Spritz with whatever you got every half hour or so and dig in.
You can check on doneness by just picking up the rack from end and checking the bend on them, another good eye test is looking at the how far the meat is pulling back from the rib bone.
Good luck, I'm ordering some of their product right now so I can have it ready when I get off this LoFat/NoFat diet post surgery.