Couple of days ago, I hit upon a great way to whiten engraved marks in steel
dials and such. "Whiteout" correction fluid.. Daub it on with just the
tips of the bristles. Then scrape off the excess with your finger nail.
Finally clean up the surrounding area with very gentle swipes of almost dry
acetone on a rag. You want to swipe over the mark with just enough acetone
to remove the excess Whiteout; dry enough to not soak into the whitened
depression.

Special paints are made for this, but Whiteout is quick and cheap, and
fairly long lived AGAICT. On my spin indexer, I whitened critical marks
such as the ( ) pointer, and ( 0 ); and geometrically significant numbers
like 60, 90, 120, 180, 240, 270, 300.

Bob Swinney