A particle system is definitely the way to go - the built-in ones (Particle World, etc.) aren't nearly as good as Particular or Wondertouch Particle Illusion, a freestanding or plugin package. While Particular comes with number of presets, I don't think any of them are impact dust like. Illusion - depending on the version you buy - gives you access to vast libraries of effects, and impact dust is most definitely in one of the libraries, along with dust trails (POV), and a large number of other effects, from spouting water, to explosions, to fairy dust - you can look at a few of the library looks on their website. You can also build your own effects from scratch in Illusion, as well as in Particular.