I use Renaissance wax with a little lamp black added for that black background look. Clean off the engraving with acetone then give the engraving a couple of coats of the wax/black, with a finger tip, wiping lightly with a paper towel each coat. I give a couple more coats of clear wax as added protection. The wax can be had at GRS as well as other places. I get the lampblack from lmii.com, a luthier supply business in CA.

Sam Welch