Ah sorry...
There is actually a detailed few pages on the particles. I didn't write it though.
http://wiki.visionaire-tracker.net/wiki/ParticlesThe link on the manual page is what I wrote when I created the manual page.
P.S: when I say a few pages, I actually mean quite a lot. I believe Simon wrote the particle pages, or maybe it was David - I forget. They've been there for ages.
P.P.S: I believe Simon intends on replacing / updating the particle system in a future update so that it's possibly easier to use yet more flexible. Something like that.