have been using simichrome for years.
it is NOT abrasive enough for the corrosive scale.
the 'crud' must 1st be removed.
i use a fiberglass 'auto detailers' pen, like those used in prep for touching up paint chips....
a/s suggests using a 'plastic scrapper' (credit card) for this first step.
then i follow this with a pencil eraser,
followed by a tiny bit of abrasive polish and THEN some mild polish (like simichrome) on a q-tip...
this can be covered with spray or dab on clearcoat, nail polish or hard poly sealant....
for the most part, the process is EXACTLY like fixing a paint chip,
except that the crud must be removed first, by 'controlled scraping' with something softer than aluminum.
because simichrome has a small bit of wax-like content, it really need to be CLEANED OFF with a solvent...
IF planning to apply touch up paint or nail polish, otherwise those layers will not adhere properly.
also remember that these modern units have brushed skin appearance, so the goal isn't shinny bare metal spots...
so the glass pen and eraser keep the brushed look, while the polish is really for the clear coat perimeter....
all of the true things that i am about to tell you are shameless lies. l.b.j.
we are here on earth to fart around. don't let anybody tell you any different. k.v.