Flesh-scrapers and stretching boards are about as primitive a tool as you can get, but it's still the most effective way for getting the flesh, cartilage, and fatty bits off of the pelt so that it can dry thoroughly.  A flesh scraper is basically what it sounds like: a short and sharp blade that's used to scrape the flesh away. In a pinch, you could use a big kitchen knife that's somewhat dull, but it might be a little more difficult than with a scraper. Hog scrapers, single and double-handed scrapers are all common. Metal and wooden boards are both commonly used for the job. If you use a wooden stretching board, you'll also need staples or push-pins to secure the pelt when you're ready to stretch it for drying. Wooden stretching boards can double as "fleshing boards," providing a nice surface to scrape the pelt on. If you have a metal stretcher, you'll just need to use a bench, table, or other flat surface on which to scrape the pelt. It's usually recommended to let the fur alone to firm up the fat some in a cool environment (about 55 degrees F, or 13 C). This will help to make the scraping job a lot easier. You can flatten out the pelt onto the board, fur side down, to let it dry for several hours before you get started scraping. When you start, the whole process of scraping itself shouldn't take more than 15 or 30 minutes. Using firm pressure, carefully scrape the fat and connective tissue away from the skin using the scraper. There's not much of a secret or a science to it–you're basically just scraping. Be gentle to avoid tearing through the skin, but be firm enough and even enough to get everything off. The tail is usually the most challenging part, so most trappers will start there, spending the most time making sure that every bit of fat is evenly scraped away. After removing the fat from the tail, scrape directly up the middle of the pelt, in a stripe. Go all the way up until you've scraped everything off a narrow strip up the middle of the pelt, and the head of the pelt. Then go back and scrape outward, extending evenly to the sides. This will help start the stretching process and flatten out the pelt. Keep using even pressure and slowly scraping off all the fat and other bits as you work. It shouldn't take that long, but be thorough. If you miss anything, you risk ruining the pelt with rot. Metal stretches are usually one-peice mechanisms that allow you to secure the pelt easily without additional tools. With a wooden stretching board, you'll typically need to use push-pins or staples to stretch out the pelt.  Stretch the pelt tightly, so it flattens out and looks clean, but not so stretched that it thins out the skin and makes it look weak. It'll also shrink some while it stretches, so you want to make sure it'll be able to comfortably. The pelt should be starfish-stretched out, all the limbs and the tail taut and extended. Don't let the arms hang loosely, or the pelt won't look right. 55 to 60 degrees F (13 to 15 degrees C) is the perfect drying environment for a pelt. Make sure it's free from sunlight and temperature fluctuations. Depending on the climate, pelts should hang for anywhere between a day and a week. You'll know it's done when the skin is firm and taut, with a plastic-like touch.
Get a scraper and a stretching board. Let the pelt dry some until the fat can harden. Start scraping the fat away from the tail. Remove the rest of the fat. Stretch the pelt onto the stretching board. Let the pelt hang in a cool dark place.