Longtoke, what are you using for finish and how are you applying it?
I always wipe on the finish on the riser. I usually spray the limbs with Helmsman spar urethane. Any overspray onto the limbs gets sanded off. The throat of the grip is the hardest to get cleaned up when sanding but runs are not a problem unless you are getting sloppy when you put it on. I use a maybe two inch square of cotton cloth, folded in half and wetted with finish. I make one pass per coat and do it under bright lights so that I can see how the finish is laying down. If a run occurs, I let it cure good and hard and sand it off before applying more coats. If you keep the runs sanded off and wet sand fairly often, your finish will be pretty smooth prior to the final sanding. Once you start buffing with the drill and cotton wheel, it will be as smooth as glass. Just be sure to buy a wheel large enough to reach down into the grip throat without the drill chuck rubbing on the bow.