Like I did with my Volt, I painted my Bolt EV calipers while they were new and shiny.
I use an expoxy paint system from G2, bought on TireRack. They seem to have the best price. https://www.tirerack.com/brakes/category.jsp?category=Caliper+Paint
To paint the caliper, you have to take the wheels off of course. I used two GM SUV scissors jacks from a local salvage yard. And wheel chocks of course. Car in P and parking brake engaged.
The kit has a nasty brake cleaner that I'm sure would take years off your life if inhaled. Hold your breath while using in an open air area. Before using the cleaner I taped all the rubber and plastic pieces so as not to soak them. I also made some simple corrugated board cutouts to limit cleaner over-spray on the upper half of the brake and suspension parts.
A piece of corrugated was used on the pavement to catch the drippings. I immediately removed the painter's tape after cleaning the calipers. The cleaner makes the tape very gummy.
I repeated the process on the other wheel.
While the two wheels where off, I applied a very thin film of anti-seize to the wheel surface that contacts the steel hub. This prevents the aluminum wheel from getting stuck to the hub via galvanic action, especially here in the winter salt zone.
I bolted both wheels back on, lowered the car, repeated the cleaning process on the passenger side wheels.
When those where done, I mixed the reactant into the paint, stirred, waited 5 minutes like the directions said. When you look at the small amount of paint, don't panic. You'll have about a third of that left over! After 5 minutes, I stirred again and then used the included brush to carefully apply the first coat on the passenger rear calipers. Don't get any paint on the brake rotor! Use a piece of paper for masking in any tight areas close to the rotor.
With first coat on the rear passenger, move to passenger front calipers and apply first coat. After you are done or in 15 minutes whichever is longer, put a second coat on the rear. You can go a little thinker for a smoother result. Then do the front's 2nd coat.
Put the wheels back on (line the wheel rim with paper below the calipers if you are concerned about paint dripping).
Repeat the process on the driver's side. Jack up, remove wheels, paint. The whole process can take hours. I started about 5 PM, was painting around 6 PM or so (less sun and heat), and finished in the dark using LED lights which worked great.