I'm getting frustrated, I used a black Sharpie permanent marker to mark the frets before crowning. As soon as the marker dries I can't see it anymore. If I move back and forth looking at the fret I can see the light reflecting off the fret surface and can "kind of" tell where I'm at with the filing. I have good lighting. Maybe my eyes are worse than I thought. Is there a particular marker someone can recommend for this purpose? These frets are the Jescar gold frets. That black Sharpie just disappears. Arrrgh! I'm stopping for today.