when grinding any of the materials discussed below, wear a decent respirator.  This stuff is BAD for your lungs.  Especially
all of them.  Especially carbon fiber.
Micarta:
Micarta, also known simply as "phenolic" in the generic grades, is great to work with.  It can be cut easily with a wood cutting
bandsaw, (a sharp blade makes it easier) ground nicely on your belt grinder, (sharp belts, you get the picture) and drilled readily.
  Avoid overheating when cutting or shaping.  Like G10, the pieces you usually get  will have a very nicely flat suface for you
r tang side of the scale.  Just rough it up a little with 80 grit or so before gluing.  Sand to 600 or so and buff with white or pink
compound.  Lighter colored micarta, especially ivory paper, will easily discolor if sanded or buffed with anything even a little
dark in color.  Red aluminum oxide paper, sanding by hand to a high grit finish, and buffing lightly with white rouge work well
on ivory paper micarta.

The hard part about using micarta is that it clogs belts up very fast.  I keep a compressed air nozzle in the grinding room, and
blow the belts out to clean them as necessary.  A rubber belt eraser works very well to keep micarta dust out of a belt, too- just
don't pay too much for one as they wear out quickly.  I believe McMaster-Carr has good prices for large belt erasers.

Ken Onion tells me (I have not experienced this personally) that phenolics can absorb and hold unpleasant smells, such as
in butchering operations.  I would at least be careful to always keep handles cleaned of quickly after heavy meat or fish cutting.

Bead blasted canvas micarta is super grippy for a rough and ready field knife.
G10:
G10 takes the edges off of cutting tools a lot worse than micarta. It's very easy to work with otherwise. It will dull your wood
cutting bandsaw blade very quickly. I have had more success using my metal cutting bandsaw to cut it with.  As with micarta, 
lighter colors of G10 require care in polishing to keep from looking "dirty."  Sand to 600 or so and buff with white or pink
compound.  No finish necessary, although wax and light oils such as WD40 are used for looks by some. 

Some colors such as "Jade Ghost" or "natural" G10 are translucent, and if there are any dark areas on the tang, such as
post-HT darkened hollows in the tang from tapering, or "epoxy rivets" to lighten the tang/improve bond, they may show
through the G10 as dark spots. Thin grades of G10 are being used now as a more stable alternative to vulcanized fiber liners for scales.
 

Carbon Fiber:
Carbon fiber is as much harder on cutting tools than G10 as G10 is than micarta.  It will likely waste one of your metal
cutting bandsaw blades to do one handle's worth of cutting this stuff.  It's very bad for your lungs to breathe this stuff. 
Some guys have complained that grinding it gets tiny slivers of it on the skin (think nettles) although I have not personally
experienced this.  Then again, I've not used it much.  I do think it looks cool, and it's surely strong stuff.  Finish like G10.