Josh, you really shouldn't need to do anything to the friction surface or worry about it at all, and I'd strongly advise against using any treatments of any kind on those porous surfaces - the minimal flash rust that might happen sitting over the winter will be taken care of by simply using the brakes - many vintage vehicles here spend the winters sitting, not a problem - if you're fussy, pull the drums when you get back to work on the truck and take a look, a light buff with fine emery cloth would be the most that'll be needed
Bill
