Preparing Gamescience dice?

So I finally did what I've wanted to do for a long time and sprung for a set of Gamescience dice, and I figured hey, if I'm gonna do it, why not go all the way with it and get them un-inked, to really make them my own? I ordered a standard seven-die set plus three extra d6, and went and bought a couple of extra-fine paint pens and some 600-grit sandpaper to use. The first thing I'm wondering is whether the sandpaper is fine enough to not damage the dice while getting rid of the blemishes. I saw some people online recommending 1000-grit, which I couldn't find, and others saying you could just do it with a craft knife; I assume it'll be fine, but I want to be sure.

The second issue is, upon checking my order again, I realized I'd mistakenly ordered the three extra d6 already inked, with white numbering. I wasn't initially sure whether I wanted to ink the set white or gold, but now I'm leaning more towards gold, so if I wanted them all to match, I'd have to find a way to re-ink the extra d6 somehow. I looked up a couple suggestions on removing ink from dice without damaging them: some suggested nail polish remover, but others have said that burns the plastic, which I want to avoid; one source recommended Mr. Clean Magic Erasers. Alternatively, is it possible I could just apply gold paint pen over the white ink that's already there, and have that be visible? Any advice?