A couple things that helped me:
1. Don't wait until the pods have completely split open and the floss is in the breeze. Pick the pods which are cracked open, but not wide open.
2. The seeds develop in an orderly state. I have found if I peel off one side of the pod I wrap my hand around the section of seeds and floss and slowly peel off the other. half. The contents still held firmly in one hand. with the index finger of the other hand I pick off the seeds. They fall off easily with a slight touch.
I never get every seed from these pods. I get about 90% of the seeds and then it starts to "unravel" and I throw the rest into a deep garbage can. So...this only works if you have a LOT of seed and are willing to part with some of it.
If the seeds aren't dark and mature, they stick to the floss. Not good. If the pod is overly mature you have floss and seed everywhere.
So...this may work or it may not...just wanted to share. I added this picture so you can see the seeds in the pod.

I'm a bit late with another option but thought I'd add my method to the discussion. I use a one gal size, soft clear plastic food storage bag to help me remove the floss from large amounts of milkweed seed. I put the seed with floss attached into the bag, use a twist tie to seal the open end (keeping air in the bag to keep it inflated), then shake the bag. The floss will detach and float in the bag and the seed will drop to the bottom. I keep shaking until it appears most, if not all of the floss is detached, then open the bag outside and let the floss float away. The seed is caught in the bottom of the bag and can now be moved to a storage container.

~Mary

I use something close to Heidi's method. I open the crack and reach in with my index finger to detach as much of the seed as I can while it is still in the pod. Then I pull out what is left and hold tightly to the middle of the mass of floss to keep it from blowing around. Remove the rest of the seed and drop the floss into a deep garbage bag. It might also help to have a spray bottle of water close by to spray into the garbage bag when the floss tries to float up and out. It amazes me how efficiently nature has designed this distribution mechanism. We could learn a lot from nature, if we paid more close attention.

Martha

I use a shop vac. Pick the pods before they dehisce and let them dry completely. Then put on a good dust mask and use the shop vac to suck the seeds out of the pods while keeping as much of the pod from going in. If your vac is anything like mine, the seeds will fall to the bottom and the floss will get stuck to the filter. Just scrape off the floss after a dozen or more pods and blow it off a bit and you're ready for the next round. About 3 times faster than by hand if you've got a large volume.

The shop vac sounds like a great idea. But, I like to do my processing while I watch TV or a movie, so the noise would ruin that plan.

Martha