47-55.1 Q's about installing 80mil sound deadener

[Livemeyer]

Got my Noico 80mil butyl automotive sound deadener, roller, tape, etc. and am prepping the inside roof of the cab. Scraped off all the old cloth-like material (is it fiberglass?) but in places it wasn't, there's some surface rust. I'm working to remove the surface rust, and here's the question: should I just put this stuff straight onto the bare steel, or should I apply a rust-inhibiting paint or primer first, or something else? I figure the sound deadener might affix itself better to the bare steel, but am unsure if it's best to leave the steel in an untreated condition.