We have found there is no one solution for cleaning bells. To get off grease and grime we have found a product called Kotton Klenser to be wonderful. You can get it for cleaning metal or wood. It’s available directly from the company or via antique shops. To remove rust we often use a wire brush with BRASS bristles. It works well on iron objects. You need to be very careful with brass bells and hardware stores sell nylon bristle brushes that sometimes work.