Very late to the game but I second what Kent said. Thats how I do it. I was also given the tip that when a few pods in the population have opened this indicates the seed has ripened and it should be safe to harvest seed. (this usually prevents you from popping open seed pods only to find them green or white, very unripe seed).
Now if only I could find a way to get the fluff on asters and goldenrods....
