Does anyone know the best way to activate light-piping, in particular for a photo? like a laser pointer or a led flashlight or something else?

 

laser pointers work great

 

I use kellogs light up cereal spoons. Just pop off the top of the spoon part and their pretty powerful. Usually they come in blue, red, and green.

Got some for star wars episode 3, and indiana jones kingdom of the crystal skull.

 

Have a lightsource behind your figure. Doesn't necessarily have to be directly behind it. I get mine off to the sides and it seems to work.

 

With some figures the lightpiping doesn't work for crap anyway. And that's if the eyes aren't bloody painted over.