Great suggetion! My two main problems with doing this specific project in post (for an animation):

1) Time and work. I would need to keyframe the lightning positions as well as a layer mask for when other objects would cover it up.

2) I would lose the light and color that it casts on other objects.

So I'll test the paint FX.

What's odd though, is that if I reopen my completed model and then add another plane with the background I have been testing, it renders the lightning in front of it just fine... after I move the plane and change my camera view, it seems to intensify the glow, which doesn't make much sense, so I have no explanation for the changes.

Maybe there is some light linking I can do to turn off the light and reflections the plane with the background receives from the lightning light node?

Edit: Tested the paint FX and it doesn't want to make the curve paintable. Also, are the only lightning brushes in the electric folder?