Use acetone, cotton balls and an old toothbrush. The acetone won't hurt blueing (not sure about nickle though).

Soak cotton balls in acetone and wipe over gold/silver stuff. Keep wiping with wet cotton balls until stuff starts to smear. Then dip toothbrush in acetone and have at. Repeat both until gold/silver stuff is gone.

Let acetone dry, wipe down S&W and oil outside and wipe clean and Bob's your Uncle!