Clear coating over soot/smoke from oxy/acetylene torch

[Nikwho]

Ok, long ago I met a custom chopper builder/painter that would use an oxy/acetylene torch running very rich and use the heavy black smoke over templates to put flames and such on his custom bikes. I have a similar idea for my car. However, in the interior, so not to take full abuse of the weather and elements. Any thoughts on what kind of clear coat product I should use to attempt this? I need a clear to spray over the soot that would be applied to the paint. I hope im making sense!

Oh, also, my car is gutted and on a rotissere, so no risk of fire.