I making two fireplace mantels out of a 100 year old white oak beam. Wife wants the cracks filled. Should I do black, brown, or clear? I am very uncertain. There are large wood borer holes and other defects and I plan to leave them unfilled. Also I would like to wire brush before a "Flater than Flat" finish. Worried about how the wire brush will scratch the fill. Maybe I can't wire brush.