Simple methods to make brass & copper jewelry shine again:
Baking soda
Apply it on the product and rub it softly with a gentle cloth. Then rinse and let it dry.
Lemon
Squeeze a lemon and rub it gently over the product. It will clean the stains and will make it shine again. Rinse and dry it with a soft cloth.
Vinegar
Apply it on the product and rub it softly with a gentle cloth. Then rinse and let it dry.
Dishwashing machine
Put your brass & copper jewelry in the dishwashing machine. Wash it like any other vessel and take it out when the program is finished. It will shine like new!