this is where i got mine from
http://www.matt-pack.co.uk/
2 litres per coat on a full subaru size car he says, but he is a pro sprayer so i would think first time you might use a bit more wasteage
but if you go to the dip your car forum some of the stuff they are doing is immense, after holiday im doing my alloys a bit different colour, still kinda subtle but not what you would expect lol