You'll have better results using an alcohol based stain like Chestnut Ridge. It works on old dark wood as well as new unfinished. Try Dollar General clear ammonia for cleaning and degreasing which won't hurt anything. I wouldn't touch coachwood or any wood for that matter with any kind of oven cleaner, caustic or otherwise. Use raw linseed oilinstead of boiled. It penetrates and isn't filled with chemicals to make it dry quicker.