I don't wood burn, but write on my bows and arrows and haven't had any problems with smearing or it becoming blurry. I spray a light coat of polyurethane on the area to be inscribed, allow the poly to dry, and then write over the area with a india ink pen. Once done I again spray, not wipe, on an additional coat of poleurethane. If you wipe on the second coat you will smear off your inscription, but with a light dusting spray of the poly the inscription stays crisp and clear.
-Dan