To paint the Earth, Moon and Mars CNC forms with matte tones of grey I used Dulux tester pots and chose 3 of their grey shades, with the lightest being almost white for Earth. I originally was going to spray the pieces and whilst this may give a higher quality finish, for these initial test pieces I decided it was overkill and too expensive. Instead I used a sponge to give the surface of each of the forms a nice texture which will give a similar effect to spray paint. I also quite like the textured surface as it seems to absorb the light in some areas and bounces it off in others.
The first coat-