Reading reviews of the GemPro 250, it seems that those who have found it to work well for them have done a few steps to great detail during set up;
Make sure it is as perfectly level as possible,
create a vibration proof mount- some mention marble slabs as used in laboratory scales.
ETA:
having the scale continuously powered(at least for 24 hrs) to keep it 'warmed up' eliminates drift.
The trickling issues seem to be caused by the fact the weighing mechanism is inherently sensitive to achieve its precision, and thus there is added damping- either electronic or mechanical.
The damping causes a fair bit of time lag for the weight of the added kernel(s) to be displayed.
One user said he got good results by removing/ reweighing the powder laden tray after every addition of powder. It apparently gives accurate results much quicker than waiting for the additional powder to be cognized by the mechanics/ electronics of the scale.
I bought this scale sometime ago with the intentions of using it for precision loading, but have yet to even unpack it.
FWIW- bought it online @ Old Will Knott Scales
To quote the philosopher John Lennon: " Life is what happens when you're busy making other plans.
I look forward to playing around with a set up/ installation when I have time.