Spraymax two-part rattle can clear for a bunch of parts like top and bottom tree, fork lowers and case and valve covers.
That's the special-second-compressed-part-hidden-in-a-can that a link was floating around a couple months ago? German company? Please report that and other uses of this product.
I can't imagine even bothering to look under there much other than to scrub it or you were a week before a show or something. Then paint it. That is a harsh place to be on the bike, but the metal there is substantial.
I found an 'industrial' rustoleum latex that I sprayed on my battery box after blasting. The thin metal parts are more suceptible and in need of attention on the 35 YO's I have found in my posession. That said, I have also been using it for touch up on the weld backbone of the frame, instructions say apply directly to surface w/o excessive rust removal. It makes an inky colored black and nice gloss. Can use your finger or a testor's brush or foam to put it on an requires no blasting away of the good paint that's there.
By the way, I also found some paint that is just a shade lighter than the color of handlebar controls. Anyone got a name for
that color once it fades down a shade or two?? Or the original dark control color?