Brock,
The Makita wheel brush sander is what we use. It doesn't do very well on pencil lines or bad stains, but it does remove a lot of dirt and loose fibers (splinter opportunities) while retaining the rough sawn look. I like the coarsest nylon brush. The wire brush can leave it's own marks that I don't particularly like.
Otherwise, Emmett is right. Scrub it with a brush and eraser.
Good luck,
Gabel