Tempera

Experimented with 'tempera' aka poster-paint last night, and the results were less than desirable.

If you're looking to create a model with realistic looking peeling paint exposing the color beneath, then go for it. Perhaps mix it with a bit of acrylic to give it some pull. By itself however, it just doesn't stick to styrene.

Wood may be a different story, since its ultimately made for paper and not plastic, but even then I suspect it may be easier to make it look distressed than acrylic.

What I may end up doing with this particular model is painting over the acrylic-tempera layer with straight acrylic, to give a bit of a 3 dimensional surface where its obvious a coat of 'new' paint was applied hastily over a previous peeling coat of paint (people do it, you know they do). My thought is that the new layer would help bind the previous layer, or at least the parts that had "stuck" well enough to have not flaked off prior to repainting.