i have a kief box with 2 screens. I handshake it for the first screen to sift. Then the second screen I put my supersonic toothbrush on the screen. Works very well. I have been looking for a cheap small supersonic motor with no luck.
i worked in a qc lab at an asphalt plant for a few years... we would have to run all the incoming aggregate as well as our asphalt mixes through a stack of sieves.
we'd put the agg in the top sieve then set it in this box contraption that had a device on the bottom that would spin the sieve set in circles and little knockers up and down that box that would give a hard knock on the sieve set to bounce the material around.
it's funny seeing these sieve contraptions because they are pretty much the same deal - spinning around, but without the metal knockers, which really does help.