You shouldn't need anything to seal or coat a polished micarta surface with, unless the quality of the laminate is poor.
Working with white paper micarta especially drove me nuts until I worked out how to do it.
Basically, it's like polishing anything else. You start with a low grit abrasive, then finer grits until the surface is not rough enough to retain smudges, and has a nice luster.
So, I usually shape and pre-polish with the machine up to 220 or 400, then start by hand with 280 grit paper backed with an eraser glued to a wood block, to sand and blend the grip. Use strong light to make sure any deeper scratches are gone.
At this point with light phenolics or G10, it will look smudgy. As long as you have it sanded out to 280, that's fine for now.
Go to 400 until uniform. It will still smudge easily.
Go to 600 until uniform. When finishing the 600 step, have clean hands and change paper frequently. New, sharp paper helps not to drag metal dust onto your phenolic when sanding pin/scale or guard/scale joints.
Buff with white or pink. A muslin wheel should work fine, or whatever really. Just don't use an old, dirty wheel. Try to keep a white or pink wheel separate for lighter handles, or at least rake the wheel well and apply fresh compound liberally before buffing. Use a new wheel if you must.
It should not take much buffing at all to bring your micarta at 600 grit up to a nice luster. Inspect the handle after buffing. Deep scratches will stand out like a sore thumb after buffing, finer scratches will look cloudy or smudged. Just go back over any such spots with the appropriate grit paper, and finish them with 600, then re-buff.
I've finished ivory paper micarta with this method, no sealer/glue, the knife was used to gut and skin wild boar, and the copious amount of blood involved didn't stain the handle. Seems OK to me.
If you are interested in "sealing" your micarta, Ken Onion showed me a method of applying carnauba wax with a clean buffing wheel that may give a little added luster. I don't use it, though.