First off, if you put metals into solution, be it vinegar or some other acid, (vinegar is an acid) it forms a hazardous mixture. It will need to be treated and handled the same as any other acid used to dissolve metals.
For less than $10 I can buy a gallon of Hydrochloric acid and a small bottle of peroxide and be able to run a LOT of fingers and get the same results. And with care can reuse it several times. Add and aquarium air pump and speed things along with out the need for peroxide, even though it does kick start it a bit better.
As for the eBay ad, I have no idea if they is using a vinegar formula or not but better options are available on this forum for FREE! All it takes is some reading.