roughing up neutron micarta scales?

Easy just hit them with some 60 grit sandpaper.

 

I think a checkering file used skillfully would yield a very nice result. Files are available in a variety of lines-per-inch so you can choose your coarseness.

 

Personally I think well-applied checkering would look better than 60 grit roughing. How about bead blasting?

 

By bead blasting I meant air pressure blasting with glass bead, but I don't actually know if that works. I've never seen it done to Micarta. It makes a great matte finish on metal however, so if you don't like the idea of fine checkering I thought it was worth exploring.

 

Just use some 320 grit sandpaper on them.

 

I use a sanding 'sponge' in the 60-80 grit range. It'll roughen the surface a bit, and you can always sand it finer.
If you want a balance between the two, use something finer than 60 and only stroke in one direction so that the micro grooves/gouges align, or do them cross-hatch, just don't use circular motion and be sparing.

Also, don't huff the dust.

 

At 60 grit, you may as well scrub the handles on a sidewalk!
Micarta only heeds the sheen removed to be very "grippy."

 

For sure!

I scuffed up the handle of Yaxell Dragon Fire gyuto very lightly some 600 and it turned out great. Just needed that high gloss knocked down a touch.