option 1
create it by duplicating polygons in your models animation and applying a slight alpha or opacity to them, this means you just play the model, no more to worry about.
option 2
program the effect by exporting the sword once with a different texture and opcaity set.
use this extra sword multiple times to achieve the result, using limb finding commands to place the sword at the right position/ angle etc..
option 3
if you want use a shader to acheive the same result, not everyone has shaders tho.
option4
thats in your head!, not mine
If no-one gives your an answer to a question you have asked, consider:- Is your question clear.- Did you ask nicely.- Are you showing any effort to solve the problem yourself 