IFB does benefit from a skim coat of refectory coating. The high carbon monoxide content of fuel gas firing tends to age IFB prematurely. There are a number of coating which will also improve the efficiency of your Kiln. Any area with direct flame contact should be lined with standard fire brick or minimally coated with refectory cement.
The suggestion of surrounding the kiln with insulating blanket is excellent. There is a hardener which will firm the outer layer of ISB and make it more stable. In the past I have built shelters around my units from salvaged galvanized duct work and never found the metal dangerously hot when protecting layers of ISB/IFB.