[WJW]

I was thinking more about "tossing a salad" type vibrations that get high enough to completely get all the particles airborne, possibly with some sort of mechanical structure above the mixture interfering with the mixing. If you just vibrate everything in-place then all the smaller particles will obviously just fall to the bottom.

I got curious and found https://making.com/equipment/high-frequency-vibratory-mixer, but that is for liquids and not for solids.