Animating light trail

I lost hope that I can do this correctly on my own. I’m trying to make that light smokey trail like this:
That butterfly leaves it. How can I recreate it in blender? Millions of particles, smoke simulation guided by particles, particles with motion blur… I tried it and It didn’t give me acceptable results. Any ideas?

An emitter outlining the desirable shape can handle distribution

It’s something different. Like, some parts of wings are leaving motion blur trail that is affected by turbulence force field or something. I could use milions of particles, to make individual particles indistinguishable but my computer won’t handle it.