I didn't read half of this thread forgive me, but the best thing I've ever used on my cast iron was Liberon Black Bison Fine Paste Wax Neutral. I've been using it for years and no rust, very slick. I cleaned all my tables down with a wire cup brush on a grinder first (I then used the cup brush to put on a faux scraping pattern) then applied the wax and buffed off. Comes off very black so I think there is a passivation reaction happening too as a bonus. It's great!