Rust removers are Phosphoric acid... you can buy it a HD in the paint dept. After scraping off what you can get to, spray it on. I've had good luck with spraying used diesel engine oil on rusted surfaces. Another product that seems to work and comes in aresole cans is Fluid Flim.
You can also buy a kit that comes with a suction air gun that could be used to spray on the Phosphoric acid.
http://www.ebay.com/itm/Fluid-Film-1-gallon-Undercoat-Kit-with-Fluid-Film-spray-gun-2-Bottles-brush-/181969928686?hash=item2a5e40c1ee:g:wxUAAOSwYaFWeZXv
