To clean cast iron pans that are deeply burnt after cooking bacon, use coarse salt, white vinegar, baking soda, and a dishwasher. Step 1. Generously cover your cast iron skillet with salt and baking soda. Step 2. Pour some vinegar, and leave it for at least 10 minutes. Step 3. Remove the weakened grease using a scrubbing pad or a stiff brush. As soon as bacon grease starts falling off, pour some dishwasher and proceed to scrub. Step 4. Wash your cast iron skillet well with hot water.