Remove the bare copper PC Board from the plastic being careful not to get oily fingerprints on it. Place it on a clean, suitable spraying surface (newspaper or cardboard are great). Using flat black spray paint (I used Krylon brand) coat the copper 3 - 5, allowing time for each coat to dry before applying the next. If your PC Board is double sided, be sure to repeat this step for the other side. By the end of this step, your board should look completely black, no bumps or unevenness, and certainly no copper visible at all.