I was wondering if Fog fluid would work? I know it has to get pretty hot, which I don't think would be a problem, but in the band we use a fogger for our light show effects and was always wondering if anyone ever tried it on RC planes. of course it might dissipate pretty quickly in a breeze, maybe not, I know I breathe it in for quite a while on a good blast of fog when were playing Comfortably Numb lol
I believe its a mixture between 10 to 75% glycol to water depending on how dense you want the fog from what I've read about it.
I was always told that a 40 sized motor wouldn't produce a good enough smoke for any type smoke system, which was all we ever flew back then so I've never tried. but now I have bountiful of engines that could produce smoke, so this year i might finally try one on my Fokker Tripe with Zenoah G26.