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Verdigris is soluble in a solution of alcohol and lemon juice (citric acid). For BRONZE, compounds containing citric acid will 'hasten' the removal of the verdigriss - copper acetate.
Best for 'polishing' BRONZE is to first sand down flat - down to 1000 grit, then use a buffing wheel and jewelers rouge. Remove all oils, etc. with acetone, etc. then multiple spray coat with clear urethane, then flat sand and 'polish' the urethane with Finesse-it™ or Perfect-it™... will last about 3 yrs. in exterior applications.
Just as the ancients did to polish BRONZE, those who clean 'museum' bronze use a mix of: pumice, beeswax, wine, salt and lemon juice .... then apply many thin coats of hot olive oil and beeswax so that the bronze turn brown (Copper oxide) instead of green (copper acetate).
For brass, just use an abrasive chemical cleaner .... such as "Flitz", BRASSO, or Never Dull. If there is a lot of surface corrosion, flat sand first before polishing.