I'd love it if there was a chemist who could explain how styrenes have changed since the early days - or the engineer (looking at John Mueller!) who can give some testimony about the changes over time.

I've heard anecdotal comments about current primers (Tamiya) having issues with plastics, but never experienced it personally.

Automotive formulas (Plastikote, Duplicolor) seem to be okay, but need a light touch cos they do not go on wet and heavy without consequences.

As long as you are not piling on the coats, I think it is safe to cut enamels with a midtemp for airbrushing, although it will probably affect the final gloss.