I seem to remember this was posted "over there" as a solution for cleaning fines from pellets.
https://www.youtube.com/watch?v=xmN9uF5oJGA
Yes, that's the video AE Neuman posted.
This is the drawing he provided.
I used to find dust-like material in my pit. It was probably on my food, too. One day while searing meat I saw sparks blowing up from the fire pot. It was burning pellet dust that becomes ash specks when burned out. It appears that the dust-like material in the pit is composed of unburned pellet dust that's augured in but blown upwards before igniting and pellet dust ash.
The more I clean my pellets the less of this I see.
I've sifted my pellets with a scoop that's intended to extract solids from kitty litter and I've used Neuman's drawing. Both do the job.