It's really quite easy. I've done many many cars/trucks. I use Rustoleum with a brush. Jack the tire up you want to paint (or all 4 tires if you've got enough jack stands), take the tire(s) off. I use a wire brush to remove the heavy stuff, then scotchbrite to remove the looser stuff. Take a lint free rag with mineral spirits to clean the caliper and then make sure it's good and dry. Then just brush the paint on. Let dry add another coat or two, and you're done.
Here's photos of some of my projects raging from my Ram to my Steeda Mustang. Yes the correct Rustolem will hold up to the heat just fine, a 1 quart can cost about $10, and you can paint a LOT of calipers with 1 can. Total cost of supplies with paint, brushes, cleaning supplies, etc should come to less than $25.
My 2012 Charger -
My 2010 Charger -
My 2003 Dakota -
My 2005 Ram -
My 2007 Ram with Off-Road rims -
My 2007 Ram with stock 20" rims -
My 2007 Ram with PD on stock rims -
My 2005 Grand Am -
My 1997 Steeda (the calipers were originally red, I painted them yellow) -
All of these were done with Rustoleum. It took me a few hours on each and cost next to nothing to do. No need to remove the caliper from the car. You can either tape everything off or just keep a rag at hand to wipe off any areas that you didn't intend to get paint on. It wipes off easily, but once it's dry it's very hard/durable. It holds up to everything from high temp on performance brakes, to road salt and mud on the truck.