Brooks Tanner replies: Figured wood is finished to mirror finish by using the same methods as with non-figured. Basically finish is added in multiple coats and is then wet sanded flat exposing any depressions as shiny spots. Additional coats are added, followed by wet sanding. This is repeated until the entire surface is completely filled with finish and no defects can be seen.
It should be noted that the finish thickness is still quite thin since a majority of the finish has been sanded off.
Wet sanding is now performed with increasingly finer grits up to at least 1500 grit. My preference in sandpaper over 1000 grit is Meguire’s Uni-Grit.
Wet sanding is followed by buffing. I usually start with a lambs wool head and 3M Finess-it and follow with a synthetic head (more heat) and polish. A highly figured grain, however, will not stay completely flat.
As the humidity cycles, you will see the grain movement in a glancing view. Often this movement is sufficient enough to be easily felt as you run your hand across the surface.
I have had one particular piece that was made to replicate the figure and finish of a set of speakers that has remained completely flat. This was finished with polyester, the same as the resin used with fiberglass. There is no infiltration or loss of water content. The piece is also in a humidity controlled environment. This is a mirror finish, but has a plastic look and feel.
If the question was not intended to be a finish question, but instead is a sanding question. Figured wood may be tooled dead flat (sanded, scraped etc.) but is dead fat only until the humidity changes.