Brother:

I used to think that the high heat, flexible primer coat was important, but was still irritated by the frequent cracking, even after a recent paint job. In the "Leatherhead" Group here on Fire Engineering several months ago, I found one brother who advocates skipping the primer, and instead cutting your paint with the linseed oil. I take it you read the blog article. This last paint job with the linseed oil has performed very well, has seen multiple fires in the past few weeks and barely shows even a hint of a crack. I really think the Linseed oil is the way to go. If you haven't read the blog, the instructions are there.

Ben