>> I just sow seeds and chaff together
For me sowing my own seeds: totally.
The Alyssum I harvested seemed to be mistly chaff and immature seeds even after sieving, but then I test-sprouted some. based on what I THOUGHT were seeds, I seemed to get 150% of higher germination rates. I would rather scatter a fat pinch than a tiny pinch anyway.
But when I save for trading, my ego kicks in and I want to get them clean if I can. Silly, but when it isn't TOO much work, I do what I can I can.
I tried outdoor winnowing just once! No effect or "blown away". I guess you have to pick a day with a STEADY gentle breeze. And heavy seeds.
But I like seives, like 24-mesh window-screening-in-an-embroidery hoop. Fabric or craft stores also have 1/8" nylon mesh fabric that can be held in an embroidery hoop. Kitchen strainers are 18 mesh or 30 mesh.
I like wire cloth in big, funnel-like PVC pipe adapters ("DWV Sewer & Drain Adapters", from Katlien over in the old DG). But you have to order 12"x12" squares from MSC Direct or other online sources (Big Book Pages 1888-1891)
http://www1.mscdirect.com/CGI/...
