doesn't necessarily need lots of masking, just on the front face around the outside of the cut holes, then place on piece of paper on a flat surface and spray from the back one colour, then the front the other colour, or just get a paintbrush out, but make sure to lift off the paper as soon as you have sprayed else you will run the risk of paint bleeding through (this is if you are impatient, else do the above and mask off properly)