Usually a layer of
patina is preferred for bronze coins (oxidization).
1 A
good patina "looks
good."
2 An authentic (looking)
patina helps reassure collectors that the coin is authentic.
3 A
patina (oxidization layer) protects the coin.
Wanting to have bronze coin shine like a new copper penny (1 cent), is going to put the experienced collector on edge.
To an experienced collector it doesn't look "real." They just don't come that way unless someone has aggressively removed the
patina, or if there never was a
patina on it in the first place (because it is a
modern forgery). Generally the attitude is to do no harm.
Part of the way you know a coin is authentic, is that it has an authentic patination. But I don't think even that is a guarantee.
It is possible to craft attractive patinas for bronze coins that due to cleaning, need to be repatinated. But, it is an art and not something to be dabbled with. A bad
patina job probably looks worse than no
patina at all. If there is a
patina job for a coin, the observer has to ask themselves if it was an attempt to cover up a forgery, or is it just a bad
patina job?