hello, I wanted to ask you a question, how would you do this you effect
://prntscr/4soh3q (this is a real photo)
I personally would do it like the fog particle in the starter content. You just have to use another texture + use a attractor + a higher spawn and movement rate 
https://docs.unrealengine/latest/INT/Engine/Rendering/ParticleSystems/Reference/index.html