Try what i use Stove Enamel. Its worked for the last 11 years. Failing that try high temperature paint for car exhaust headers but read the can first! their not all made the same some have nasty chemicals avoid those.You didn't say whether the rust was external or internal. If its external on the doors for example the stove enamel will work well. Rub the rust spots with emery, treat with rust inhibitor and paint. After painting the enamel has to bake for a while but i usually run the oven for a while until its hard. Now make sure that the room the well ventilated when you are doing this and while the paint is curing.
Arthur
March 2011