This is a great bait for anyone with a strong stomach. Start with a tough-skinned fish (carp works best) and fillet it. Cut the fillets in to 1"x3" strips and put in a jar. Add a few teaspoons of water and screw on the lid loosely. If the lid is too tight, the jar will explode, making a giant mess. Bury the jar 6" down in a spot that gets a lot of sun. Wait a week or two, and your bait will be ready to go. Present like any other catfish bait.
Tip: If you're up to the task of handling the bait, put a tablespoon of vinegar in the jar before burying. It makes it extra sour.