Trying to enamel cast iron of an unknown quality is a gamble. Iron can be very gassy when heated which then creates a horrible bubbly porcelain finish. If one found one that we built, depending on the skill of the factory, we have an iron composition that takes porcelain nicely. Generally a lot less bother though to fully sand blast a stove then high temp paint instead. This would avoid the whole tear down and rebuild process which takes some skill & care.
A secondary air approach is required IF the basic burn dynamics of a stove does not yield a clean burn to begin with. Our stoves burn "EPA clean" w/o secondary (air injection).
Control of the burn rate is determined by air flow volume through the stove which is determined by the pipe damper setting in relation to the stove's own "controls". Starving a fire for oxygen via gasketing to try to control burn rate to extend burn time only creates a smouldering, dirty burn. We have found that door gasketing would decrease the required air these stoves need to burn cleanly. As we have gotten to know these stoves over the years, it has become very apparent that these simple designs are quite evolved w/o the need for complicating, maintenance producing, "modern" burn dynamic approaches.
Our goal is to keep these refined designs alive which have stood the test of time that are easy to operate and maintain. Proof of these attributes and timeless utility is the fact that they are still being produced after 100 years! If you want "features", there's all sorts of stuff out there trying to compete for your attention and eventual purchase. We prefer to offer traditional elegant simplicity which also happens to be low maintenance.
Bells and whistles more often than not break! A/NSW