Here is what I would do. I would paint the hickory with black acrylic paint, thinned with water. When this dries, the grain will be raised. Then sand off the black paint with fine sandpaper and it will all come off except the black paint down in the grooves of the wood. Then come back with thin grey acrylic paint and rub it on with a cloth. Make sure that you rub it so that it will soak into the surface wood but not into the black cracks. When it is dry, then put whatever finish on it you like. I like either Casey's True Oil or a rub on poly. If you want to go "abo," rub the charcoal into the cracks, then put vinegar in a jar and put a piece of steel wool in the vinegar. Let it sit for a few days, then take out the steel wool and rub the solution on the white wood. It will turn a pretty silver grey. I learned this from making instant barnwood frames for my paintings.
