If you have an old rusted out file, of any size you like, you can grind off the side of the file where there are costomarily teeth, and then use the side of the file or rasp to scrape the large scales off the horn. Scrape from the tip to the base of the horn, and you won't mess it up. If you create a post to hold the horn, made of wood, wrapped in rags, for instance, you can jam the raw horn on this post, and then the action of scraping from the tip to the base will help keep the horn on the post. I have a coarse draw file, that is very old and was rusted before it came to me. It makes an excellent scraper for this coarse work. On a rare occasion- less than I thought when I first chose it to use as a scraper- I have resorted to useing the teeth of the file to remove some difficult spot of scaling.