What is your best method for separating? Sometimes I can put the collected seeds in a plastic container and shake a bit and the static electricity causes lots of the chaff to stick to the sides while the seed is heavier and stays on the bottom of the dish.
Sometimes I get lucky with a sieve of the right size (I have a battered one that's perfect for basil), but mostly I use the "swirl & blow" method (on a rimmed plate or shallow bowl). If you crumble the seedheads and let them dry a while, the seeds of most plants will be heavier than the chaff.
Some seeds I just save chaff & all -- zinnias, for example, I just don't have the patience to pick out the seeds, which don't seem much heavier than the larger dried petals in the chaff.
Are you saving some special seeds for the Feb swap this year? :-)