Ok, I'll give away one of my trade secrets, Old Fox's Super Goo.
Jerry Marsh at Friendship Trade Co (info in back of MuzzleBlasts classifieds) Sells an inletting blue that is water soluble, so you can wash your wood and hands to remove it when done. It works great and a small vial will last you for years.
I tried to figure out what it was made from and came up with an alternative, that is almost as good. Get some chalk line chalk, available in several colors, and either water soluble oil or permanent antifreeze. Add just enough liquid to make a thick paste. Apply with an acid or artist's brush with half the bristles cut down to make it stiff. Store it in an empty percussion or musket cap tin. It will separate on sitting, so you have to re-stir it with each use. Non-penetrating and water clean-up. Blue works well on light wood, red works well on darker woods.