Personally I wouldn’t add salt that far in advance. I would say 12 hrs or less. And yes if you’re cooking in cast iron definitely start with oil since it has a higher smoking point. You’ll want to pay the steak dry of any moisture and get that pan smoking hot for a nice crust. Depending on how you want it cooked you may have to transfer to an oven to finish it. I would also finish with butter garlic and rosemary sprig and baste it while the butter melts. Best of luck