Dennis,
The dry erase markers I have at the moment are marked as EXPO. I really can't say that I have selected any particular brand, just pick them up at Staples office supply store nearby. I actually use multiple colors at times particularly if I think I may have hit the wood wrong while moving the metal in or out. Helps me avoid over cutting areas around the breech when a barrel gets tipped in wrong. I can apply a second color and see if it makes the same contact. Usually use black, green, red and blue as those come in the 4 pack.