Vishesh is wrong!!!….just kidding his way is probably better. I like to have control of the mask I use which is why I would probably draw my mask/path then use the stroke effect.
Darby is right….keep you particle layer 2D. As long as you have tracked the position and use a light as an emitter you should not have any issues. (you do need a camera in there)
Mocha is a program developed by Imagineer Systems. It is bundled with adobe after effects since version CS4 (if my memory does not fail) It uses planar tracking technology instead of the standard point trackers.