It has long been the practice in woodworking that, to get a very smooth
surface, you do the following steps:

    1. Sand the wood, with the grain, in a progression of grits,
       starting low (60-100) and progressing up through 320 or so.
    2. Wipe the surface of the wood with a cloth dampened with water.
    3. Allow the surface to dry completely.
    4. Sand lightly in a cross-grain direction with a fresh sheet of
       the higher-grit sandpaper (320 or so).
    5. Sand a final time, with the grain, using the same grit or a
       higher one.

Vacuum the dust off between sandings, if possible.  The idea behind the
water and cross-grain sanding is that the water swells the pores of the
wood, raising the grain and any loose wood fibers.  Sanding with the
grain would push them right back down; so you lightly sand cross-grain
to cut them off.  Then sand with the grain to remove any scratches left
by the cross-grain sanding.

This preparation is much more important when using a water-based
finish, as it raises the grain more than petroleum-based finishes like
shellac or polyurethane.  I'm not sure why water raises the grain, and
the other stuff doesn't, but I've felt the difference myself when I
prep the wood this way.

I'm not sure how this all works with the graphite.

Bill Mackin
Iowa