Chafe is fine IF there are actually viable seeds in there. The problem is, if the person has been careless about cleaning the seeds, then have they also been careless about when they collected them? I received a Monarda seedhead in a trade last year, which was supposed to be from a white M. fistulosa, and I tore that sucker apart and found maybe 5 seeds (which didn't sprout). I also received Aster novae-angliae once which appeared to be a bag of fluffy chafe (it was like where were the seeds???). I sowed the chafe, and did get 1 healthy sprout. By no means do I expect perfectly clean seeds, especially with Asters which are pretty tedious to clean. But these seeds were ridiculous.

Sifting with a succession of coarse to very fine screens works for some. The very finest screen is used last to remove dust from the seeds. For some seeds, winnowing is the fastest method. If the chaff is crumbled up, the seeds are invariably heavier than the chaff and dust. I use a 12" pie pan, and just step outside on a breezy day. Swirl the stuff around and flip it into the air a couple of inches, and the lighter chaff and dust is blown away, leaving the seeds. I've also done this with a box fan. I set newspapers or large cardboard trays on the ground in front of the fan, and adjust the fan's speed to get it right. The few seeds blown out fall in the closer tray, and the chaff goes to the further one. Once you have the technique, you can do a lot of seed in a short time.

Iris - I certainly have significantly different growing conditions than you so I can only relate my own personal experiences with winter sowing. I currently have 16 recycled milk jugs winter sowed with mostly carnation varieties since they seem to be evergreen in my southern New England climate. Hellebores/Lenten roses are also evergreen here which makes them another coveted (albeit expensive) evergreen perennial. I don't want to fire off a rocket at your seed-growing strategy but winter sowing is vastly different from just sowing seeds in the dirt. It involves sowing seeds in recycled containers and letting Mother Nature do what she's been doing the most recent millennia on our planet--growing things that sustain bees, butterflies, hummingbirds, deer and other critters. The seeds' genetic code tells them when the time is right to sprout (i.e., when the hours of daylight + moisture in the growing medium + temperature trigger their genetic code). Plants tend to be significantly more hardy since they grow as/when it's natural for them to do so. FYI - I had a couple of foxes that set up housekeeping on my little green acre a few years ago. They produced three cubs. I got a kick out of seeing them every morning--early--when they came out to romp and play between 5 & 6 a.m. BTW - Select Seeds is just about 12 miles east of where I live. The owner is a reputable seed source.

I think there's a good chance that what you are calling "chaff" may be seeds. Personally, I'd just plant them all and see what comes up. Have a look at this link, and the top left pic of seeds resembling yours. The writer does mention the various shapes and sizes are common in the same batch. Some other interesting info there that may help you in propagation. I've always found Euc. seeds very easy to propagate, but YMMV... Growing Eucs from Seeds ETA...I don't consider your seeds to be tiny at all! I've grown many Eucs from seeds no bigger than dust.