Separating seed from the chaff?

Anyone have some effective methods of separating seed from the chaff? Specifically I'm interested in separating Phacelia seed from the chaff.

I separated the seed pods from the stem, beat them up with a rock until they were mostly separated, and then put them in water and threw away every thing that floated.(About 2/3 to 3/4 of the seeds sank) I have not done a germination test yet, so they might end up being all the duds.

Do you have a solid need for clean seed, or are you just doing it to be neat and orderly?  Because I've seen some serious seed savers discuss how liberated they felt when they realized that dirty seed germinates just as well as clean seed, so they stopped bothering.  Just a thought, not trying to undermine your question.

Depending on the relative weight of seed and chaff, I've sometimes had good luck just stepping out on my porch and blowing into the mixture with my mouth.

Thinking of if there is a way of easily spreading the seedlings further apart rather than have 3 or 4 seeds in a pod germinate virtually next to one another, perhaps would have more biomass per plant as a cover crop. I might just scatter as is, just separate from the stalks. Tried separating a few using water not particularly effective, perhaps I should thrash them first with a rolling pin or a rock, maybe a meat grinder might work or a liquidiser, perhaps that might be a bad idea. No need to be clean and orderly, just effective. Chaff seems relatively heavy compared to the seed.

Been a while since I harvested Phacelia seed, but if I were doing it today, I would:

Wait until the plants were dried down in the field, or starting to shatter, whichever comes first.
Pick the plants and beat them against the inside of a garbage can to release the seeds. Better yet, cut them off just above ground level so as to not introduce dirt clods into the seed.
Shake the garbage can to settle seeds to the bottom.
Rake off the bigger stems and pieces.
(Optionally dump onto a screen with big enough holes to pass the seeds and retain the chaff.)
Winnow.