And just to add something,
of course you can use the brush to make lightning effects!
Do something like this:
New layer1,
add a small 0%hardness white brush-dot to the layer.
New layer2, (drag this below layer1)
(say you want a green effect)
Add a larger 0%hardness green brush-dot to the layer.
Take out the smudge tool with 40% strenght and start smudning in and out from just outside the center of the green dot.
You can do this with the white dot as well if you wish.
Give them both some gaussian blur with filter>blur>gaussian blur.
You can try adding more layers with different colored dots if you want, you can also try with different blendin modes.
This method should work
