This method of doing a "graphite block" was taught to me by Tom Sprague
when I apprenticed under him in the 1970s.  According to him, it was
the original method that was used way back when.

First you lightly dampen the surface with pure white vinegar.  Dust the
surface with fine graphite and rub it in firmly with the base of your
palm.  Go over lightly with a single edged razor blade to remove clumps
of graphite, then dust and rub out again.  The surface will get real
shiny.

The acid in the vinegar breaks down the graphite.  When the vinegar dries
during the polishing process, the graphite molecules fuse together in
the wood, making a hard durable and smooth surface.  It will actually
feel like highly polished marble.

I have tried other methods and have found this to be the best, for me.
Try it!

Brian Thornton, Short Mountain Music Works
http://www.mindspring.com/~goatboy/smmw.htm