Amaranthus, Chinese Spinach, Fountain Plant, Joseph's Coat, Summer Poinsettia 'Perfecta'

I received some seeds for a 2011 summer crop of several colors of this plant. I have collected the stalks with the brown flowers on the ...Read Moresides and now wonder how to collect the seeds. I have shaken them but the best way seems to be to rub the blooms and the black seeds fall out. However, the pieces of the flowers are extremely hard to separate from the tiny black seeds. Does anyone have any advise for me? I have a lot of these stalks to deseed and would love to find out the proper way to do this. Thanks all.