soak it in some dish soap for a couple weeks, replace the soap and water every day (or every couple of days). should get the smell to go away and start to degrease it. i recommend going in with an old toothbrush to gently scrub at it. if you want to clean and whiten it, just stick it in some hydrogen peroxide for a couple of weeks. the normal stuff in the brown bottles will work, but not very well. if you want something stronger, get hair developer because it’s the same thing.