I think your best advice was from coppercoins (was that on the other forum?) to just use oily rags from a JiffyLube or a similar establishment. Just make sure that you ask for a "clean" rag. It will still have latent oil in it and it should do the trick. Really, Mike should know since he's spent the vast majority of his life looking at copper coins!
10 years late on an answer but soaking Palmolive Dishwashing Liquid will darken fresh copper. Use a mild acid to clean the cents, then soak in the liquid.