like allways, there are differend ways to make FX. Some are good some are "not so good".
I would try to track the tip of the sword.
Parrent a little Masked-Solid to it.
Add a adjustmend layer, with an Echo effect.
Play a little with the settings and look at it.
I would be aware of this FX bevore shooting a video.
Put the aktor in front of a little green screen.
Let him/her perform.
Key him/her out in post.
Trace the siluet.
(Don´t know the correkt englisch word for PAUSSTIFT - it´s found unter LAYER / and then down the menue, just over PreCompose)
Use the new layer with - Displacement, vector-blur...
Change the overlay mode to add or multiply.
i´m aware that this is just a rought way, but, you didn´t even told us what your footage looks like... so this is the route - finde the way home by your self - good luck!