We have two metal polish products available on our store. Please make sure you take time to select the appropriate item to get your best possible finish. If you are unsure, feel free to contact us with a description & photo for  our recommendations.
Wenol Blue Ultra Soft - For all newer bells that have lost that showroom finish (Finishing Polish on Coated Surfaces)

Wenol Red - For all old bells that have become oxidized. 
Multi-purpose polisher 
(Not suitable for anodized or lacquer coated surfaces.)

Use multiple ultra soft thin rags to gently buff back to polished state, remembering to be gentle as the thin coat of lacquer acts as a shield for the brass. If the shield is broken you may need to polish more vigorously to get your bell back to your desired state & finish with a new lacquer coat to seal your hard work. Polish with multiple light circular strokes to help preserve the life of your bell. I have found a Ultra soft buffing ball on the power drill to be most effective & non destructive.