They do sell paints that are specific for brakes. I did mine also. and the best bet really is to take apart the brakes and not try to paint them while they are on the car. Take them apart, clean them really good. If you can take them to a shop and have them sand blast the parts for you to make sure they are completely clean. Make sure to get primer also. (they have high temp primers as well) and paint them with light coats of primer and once that dries apply the color.

Delsol... you can take off the rear drums and get them sandblasted and try again. If the paint flaked them it's because the drum was not completely clean, any old paint, rust or dirt that stays under the paint will push up the paint, so having them sandblasted would help.