Haven't learned particle scripting for ArmA2, but I can help you with a light source that will affect the environment.
_light = "#lightpoint" createVehicle getpos mylightspot;
_light setLightBrightness 0.5;
_light setLightAmbient[1.0, 1.0, 1.0];
_light setLightColor[1.0, 1.0, 1.0];
_light lightAttachObject [mylightspot, [0,0,0]]
This will create a light source that affects the game world, I use it for buildings that are not lit automatically by the game engine during night. The light effect is not visible during the day so you will need to create your scene at dark hours.
"mylightspot" can be an object of any kind, even game logic. "setLightColor[1.0, 1.0, 1.0]" is RGB colors. The other commands you can play around with for desired effect.
If you delete the #lightpoint let's say 1 second after creation it will light up the environment for 1 second. You can then maybe use a quick particle script for the flash bulb if you are really picky, but since there is no Hasselblad/Nikon addon yet (afaik) you probably won't need that.
If you don't like that you can play around with
aperture, you can create whitewash flashes (during day) for the screen with that. To make it really simple I would use the "standard nuke" WHITE OUT titleRsc.
Hope that helps,
Laggy