im starting to make one myself out of a chopping board on spikes where I have drawn threads in the feet of the air pump
so its stuck to the board and transmits vibration to the cup ( later I will try springs as feet)
the air comes from the bottom center not from the side and i have laid a rounded cotton layer
(It is just plain cotton not the pads you can get) under a filter
the filter is pressed out of a vacuum cleaner bag (so it is 2 layers)
the powder paint it expands good in the cup and got no valcano
and the powder paint:
cheap hand blender and bowl run the powder paint for 30 min.
.
the final one gets a JBL ProSilent air pump , I like the air pump regulator it got.