If they are bronze finish and have gone a rich dark colour rather than blue or green and powdery then they have developed a nice patina and should be left well alone (apart from their regular maintenance) except for an occasional wash and wipe with a rag with the *barest* hint of oil on it.
They *could* be polished bright but why wear them out sooner?
OTOH if you have thick deposits of verdigris clean it off, and try wiping on a very very light smear of Owatrol in the hope it will provide enough protection for the Bronze to develop a patina.
If they are chrome finish, all chromed parts *except* the drum face can be polished with any *good* chrome polish. (you don't want to polish where the rope goes round the drum as that should be textured and you don't want that part slipperier)
Stainless, treat as chrome or you can use a dedicated stainless polish if you prefer, just *dont* get any on Chrome!
If they are anodized alloy, you cant really polish them. Just wash and wipe with that rag with the barest trace of oil. If they are black or grey anodised they will look crappy if worn, but its of no significance. Clean, well maintained and properly lubricates is *far* more important. . .
As Lewmar don't do a composite or carbon size 8 or 16 winch, we don't need to consider what to do with those!