I am finishing a tabletop made of reclaimed boxcar flooring using a thinned shellac toner. Problem is the spray does not get in some of the hairline cracks and leaves a visible "white line" of unfinished maple. Any ideas on how to color these cracks? I'd like to stay away from epoxy if possible. Btw, I have only finished the bottom and not concerned about the white line cracks there. I have raw wood on the top and legs right now so a pre coloring is possible. Thanks in advance.