Well, don't paint parts that will rub. I assume all the items that are bolted on. A home paint won't survive, it will peal. If you'll leave at least those parts unpainted, together it will look more presentable than scraped off paint.
First, you'd need to either etch with acid the metal or use like a 600 grit sandpaper. This will help the paint adhesion. Surely you'd need to clean really well the parts with acetone (home depot), make sure you wipe off anything, it is like adding soap, wipe that lifted oil away with a lint free rag. Make sure acetone will fully evaporate before painting. Either spray or brush on, follow multi layer directions on the paint direction label. A temperature will change how fast it will dry, a humid environment might totally make the paint adhere horribly. A dusty environment might ruin the finish too.
There are places online what will paint well, look for gun related painting services. They know metal and do small weird shaped parts. Perhaps it will be the best solution.
Darn - you are right about the moving parts. So if I paint the top surfaces (the ones that are visible in closed position), it should work - when it is open, the saddlebag will cover it anyway.
There are "bluing" liquids for guns. But they only work on some alloys. Say, if that metal can be blue-ed, you can do a number of bluing sessions, it happens very quickly, you can get it to a very dark blue, almost black. But, not sure if that metal can be blue-ed.
Did same this winter. Indistinguishable from the factory black finish (my GT pillion backrest hardware is factory black.) Have used cerakote a lot on bobber parts and now the rocket. The big upside is not only durability, but it’s thickness is negligible, so doesn’t affect fitment as sometimes powdercoat can.