If you are in western Sydney go to VG paints in Girraween, if not go to any auto paint shop, give them a sample colour and they will mix+match for you .
You can use 2pack or even acryllic as long as you know how to paint .
If you are not experianced with the sparay gun ( and it doesnt sound like you are, if you were you would know how much paint you need ). If you are not experianced you will get a crap job, either runs on the job or very dull.
To just paint the covers on your RB head you only need 1/4 of a lt, but get 1/2 lt and if you are not experianced use acrylic for 2 reasons. 1) easier to use and 2) not as poisonous as 2pack .
Spray it outside on a calm sunny day at about 25 degrees is best, spray in the shade and when you finish put it out in the sun. Spray even coats enough coats to cover then another 3-4 coats after that, flash between coats . If not experianced do a trial ryn on scrap metal, if you rub the old pain off and expose the alloy you have to use etch primer first, but you shouldnt have to rub it all off .