Step by step video:
http://www.youtube.com/channel/UCWPG3YlGONcsdj2_wpUhBpQ
Took a nice but gold and silver helmet. Sanded with automotive sandpaper 80 grit then 600 then 1000. Then a black satin primer+black krylon. Then "Grabber Green" engine block paint from Duplicolor (sold at Autozo