One of the best ways would be to call a couple of autobody shops to see if they could do this for you and of course how much. I have seen this done many times on all types of metal doors, fireplaces and so on and they look excellent.
You can spray them yourself but if you have never ran a spray gun it could turn out bad.
You can paint them by hand but is a very tedious job but if you have the patiants very doable but you have to determine if its oil or latex, best way stop by a paint store and pick up one of there paint testers and follow the instructions then once you know what it is go from there.
Weather its oil or latex you should give then a sand with 15o grit sand paper, wipe them down and then go over them with a tack cloth to remove any fine dust. If its latex a top quality Ben Moore latex enamel, if its oil and you want to use oil than a top grade Ben Moore enamel.
If its oil and you want to use Latex then follow the prep I mentioned and use a top quality Ben Moore primer ( I use Fresh start ) They have it in oil or latex then sand with 180 grit paper clean and tack cloth then apply 2 coats of enamel.