I like to clean the coin but not change the color or scratch it. I stumbled on a product that is sold by coin dealers, MS 70. It says it is good on gold, silver,nickel, copper, bronze, and brass. I followed the instructions on a penny that I could not identify after a soap and water with tooth brush washing. After three applications out pop an 1876 IH penny. I was shocked at the detail the coin had. This product should work on wheaties. It would allow you to keep any coloring while removing any gummy dirt.
Ed