Not sure how well it works as I'm in the process of building my UDS. But I just primed my Weber lid with the VHT Flame Proof primer from AutoZone. I scuffed the lid with my angle grinder and a wire wheel. I tried a bunch of stuff to try and get the porcelain coating off and it wouldn't budge. We'll see what happens. Painting will only be as good as your prep work. Here is a pic of it all primed.
US Navy Chiefs...Unity, Service, & Navigation to the Fleet since 1893