2D Skeletal Animation effects

I started experimenting with 2D rigging system in unity but one thing i cant find how to do is effects, like a simple sword slash effect, does anyone know how to do these things without including the whole slash area in the rig?

I saw trail renderers but this seems to be for 3D, haven't seen anything like it for a 2D rigged animation, and it also wouldn't work since the animation isn't interpolated so is more like frame by frame, so it need to be some way of adding a sprite while animating to the rigged animation (?)
I'm completely lost with this

Here is what i mean, exept for the body, is there a way to add the white slash and the break effect with an skeletal animation 2D? 9871512--1422966--Animation from reference test 555.gif