I don't use any water at all. If you use water it will wash out any contrast. I put the coin in boiling hydrogen peroxide for a minute or less. This will get the crap off the coin. Then I will rub the coin between my thumb and finger (don't ever rub silver though). This will make all the high spots (date, face, letters) on the coin stand out. The more you rub, the darker the high spots will get. It's the oils on your fingers that make the high spots darker. If you need more oil, then run your thumb across your forehead to pick up more. Again, I use no water at all. Same for cleaning old buttons. Just rub them clean. You'll keep the contrast so the letters stand out more. Here's a picture of the last indian I found. Think that last eight looks a little funny?
-Swartzie