it's all in the prep work. I painted a set of calipers on my 911 track car a few years ago with the basic Autozone VHT red high heat paint, and it flaked right off when the calipers got hot. And I'd gone so far as to wire brush and use lacquer thinner to thoroughly clean the calipers prior to painting.
Then I used a caliper paint kit I got from Pelican that includes all the prep and paint stuff necessary. Held up well on both the 911 and an Audi I had at the time. But I did get the 911 calipers to turn brown from extreme heat.
Pelican Parts - Product Information: PEL-CALPNT-RED