This is referring to sanding scratches *in the metal itself* right? Abrading metal is very different from abrading paint and even harsh compounds can give merely so-so results. Noting that YMMV applies and we might have different standards with regard to what's good enough:
Thick-enough clear might fill the scratches OK. I used 2K to final sand some *really* nasty pitting on my beater-Blazer's winter wheels (after using a Dremel and then other papers to get the worst leveled) and the clear I applied filled/concealed the sanding scratches just fine (not that the repairs look that great, but still, no sanding scratches are visible).
Or you could just sand again with a finer grit before you clear. I'm a big fan of Meg's/Nikken's 3K Unigrit, and I also like the Mirka 4K. But they're made for sanding paint, not metal and metal loads abrasive media differently than paint does so :nixweiss when it comes to using the really fine papers for this.
