If the seed is fully ripe it should fall from the bracts by itself.

You could try rubbing in a sieve.

I strip the mostly brown bracts into a bowl and then let them dry for another day or two. I then pick up as much as I can and vigorously rub between my hands over and over to release the seeds. I gently toss, so that the seeds mostly fall to the bottom and then I carefully remove the majority of the chaff.

Lastly, I put small amounts of what is left on a flat plate, tilt to about 30 degrees and tap the high side. The chaff moves up the plate and the seeds move the opposite direction for easy collection. I repeat several times before discarding the chaff.

I get TONS of black viable seeds.

I tried using a sieve, but the holes only let a small number of seeds through. I haven't found a sieve that has slightly bigger holes, so instead I use the method above.