You want to remove the finish on costume jewelry? What is it finished with? Please post a picture so that we can see what you have to work with.
Do you mean tarnish?
Is it Sterling? White toothpaste could help
I use white toothpaste, not jel.
I sell a lot of silver on Ebay. Jewelry, silverware, serving sets. Silver polish like Wrights and dips like TarnX tend to remove some of the metal. The foil method doesn't work that great and still leaves a grey film that still needs to be removed. I use white toothpaste (not gel) and a damp toothbrush. For large items I use a damp cloth. Also works on copper, brass, gold, porcelain, ceramics, sneakers, plastics, etc. For my sales I needed one product for cleaning everything.