0000 Steel Wool. Over the years I have tried just about everything recommended here and, to my mind, none do a better job than fine steel wool. I have knocked down some very high gloss finishes to a very subtle dull glow; almost like a rubbed oil finish.
I have never had a problem with steel wool residue remaining in the finish as often mentioned in various forums as a deterrent.
I pretty much use the steel wool dry, but occasionally use a little lubricant as well.
Always wipe the stock with a dry rag after you rub it.