Go to an automotive parts store that sells paints and find some that's made for metal trim (no primer required), it usually comes in satin black and all you need to do is scuff the parts with Scotch Brite pad. Spray on a couple thin coats, you don't want it too thick or it will chip. Let dry for a few days, since you are in Australia a few days out in the sun should harden it up good.
If you have spray equipment the best thing to use would be an auto epoxy primer such as PPG DP 90 (satin black) it has excellent adhesion and dries super hard, but it's also very expensive and very toxic.