I know this isn't pertaining to Roll Cage, but similar and maybe it can help you. I refinished a few rims for my truck using a simple process: Sand down to metal - Etch primer - Primer - 3 to 4 coats of paint of your choice (I used VHT Gunmetal) - 3 to 4 coats of clear. Took me 4 days for 4 rims working on them a few hours at a time, in between other honey-do chores. Also the rims were gouged and scratched pretty deep from the previous owners failed attempt at offroading, which made up for the longer work time.
There was a lot of cleaning each time and I took my time for each rim, but the results are after 3 years, potholes, new orleans streets, and 20k miles, they haven't faded or chipped.
Hope this helps you. Also everything I found was at Autozone (cheaper online tho if you are patient).
I can PM you my entire post I had on the other forum if you want.