I've found that when painting high temp paint on surfaces that will see elevated temperatures, 1970's stove hood in a park style and various exhaust headers, the metal takes the paint better if it is heated prior to painting. The stove hood was heated in the oven to 200° between coats because that was the lowest the oven would go. The headers were heated with a small propane torch. As the metal is heated, you can see the moisture cook away. The times I tried painting without heated, I had lots of paint peeling issues.