I've got a few sets of G-10 scales nearly completed. The firstset in the pic is the set I'm trying to finish right now. I've tried smoothing out the surface with a coarse sanding pad until it looked uniform, but white/grey areas are still there when I go to higher grits. The first set is sanded to about 1k-1,500 grit.
The third scale in the pic has the unfinished side up. It just has scratches from the concrete I put it on before sawing. My goal was to get them back to that slick, solid black look when I was done with them.
Do they need work with a coarse sanding pad, or is there something else I should do?

Thanks. I appreciate the advice I've gotten so far and it has been really helpful while working on my SR's.