The standard finish used on Micarta and G-10 by Bark River Knives involves polishing the material with very fine grit, followed by applying a wax compound to the surface and buffing it to a gloss. (A matte finish is accomplished by ending the polishing process a bit sooner, finishing with somewhat coarser grit. No wax is used.)
Let's say you try the standard finish and find yourself wishing for matte. You can make that happen yourself -- using a Scotch-Brite pad and some grease-cutting dishwashing liquid, gently scrub the surface to a finish you like better.
As an alternative, of if you want an even grippier finish, you can use 400-grit sandpaper.
Go slowly, adjusting your handle's finish a little at a time. Don't use steel wool, and don't soak your knife in water (soapy or otherwise).
On the other hand, if you have a matte handle and decide you'd like to try a glossier finish, apply some paste-type car wax and buff away.
By the way, don't worry about messing up -- modifying your handle in this way won't void the Bark River warranty.
Finally, if you're not much of a do-it-yourselfer, you always have the option of sending your knife to the Bark River Spa.
(For more information, see our primer on matte vs. standard finishes.)