Most paints for polycarbonates are for R/C car bodies, and are laquers. I don't have any Testors but I have some Pactra. I just tried it on a scrap of styrene and it seemed to work fine.
I don't know what the "Smoke" color is, but I assume it's a semi-transparent black or dark gray. If you spray it on clear I suspect it would fog it. If you spray it over acrylic or enamel I would make certain that the pain is completely cured and even then try it on a scrap painted the same way first. Laquers are pretty aggressive and painting them over acrylic or enamel that isn't completely cured can cause them to dissolve.
Test it on some scrap first, but I think you'll be able to use it OK.