Hi Rob I have been a custom knife collector for many years, and have owned many knives with micarta handles, and if im honest i'm not sure you can put a high polished finish on micarta looking at the material and it's construction, it was purely used more for it's super grip affect rather than it looks, if you know what I mean, it as been used to make razor scales, but i think they are going more towards the other knife material G10, and this also applies in the knife industry G10 seems a better option, not to sure how good that would even polish to be honest. But if it were mine I would try the tested methods of up the grits, and finish of with a buffing solution, or maytbe some metal polish. good luck.
Jamie.