I have built a desk and a mirror frame from some iroko , the grain was quite interlocked and could not be made clean with a plane , a woodwork book advised using a scraper which I have bought but the books intstructions on how to sharpen and use the scraper are muddy at best , Do I need to buy a burnisher ? what is the burr , is the scraper then sharpened over this burr in the same fashion and angle as a chisel ? Any info would be great , cheers