The corrosion-removal product you used was likely an acid which etched/anodized the base metal. This sort of product is intended for metal to be painted or otherwise treated.
Filiform corrosion is usually the result of bare aluminum's natural tendency to create an aluminum-oxide covering to protect itself from further reduction. The Airstreams of this recent mfr were coated with a clearcoat product by Alcoa in an effort to reduce the need for polishing. Unfortunately, wherever an edge or scratch or cut occurs.... exposes the bare aluminum again....and creates a place where corrosion can again occur. (Filiform can also develop beneath the clearcoat where pin-hole damage exists in the clearcoat, once the oxygen gets to the exposed aluminum.)
One way to take care of this is to remove the clearcoat from over the oxidized area, polish the filiform away, clean the surface with alcohol, then re-apply clearcoat (which can be purchased in small quantities such as fingernail-polish, self-contained-brush-lids types, and also in aerosol cans at automotive paint suppliers, auto parts houses, and WallyMarts.
If you use a buffer to attempt to remove the filiform prior to removing any covering of clearcoat you will only succeed in "burnishing" or "burning" any existing clearcoat over/adjacent to the fliform. That is why you want to remove any clearcoat that my still exist directly over the filiform, before polishing-away the filiform and then recoating it.
Hope this helps.
2012 Ram 1500 Crew Cab Tradesman 4.7L 4X4