My method is to get a large, dry mixing bowl and an old sonicare toothbrush. As the male starts dropping pollen I use the toothbrush to vibrate pollen out of the pollen sacs. Then I use the toothbrush to vibrate the pollen out of the bowl through a mesh screen.
Once I have clean pollen, I dry the pollen in a dessicator. This is a very important step. You need to dehumidify the pollen as good as you can for longevity. I continue to collect pollen for about a week. After it is finished, the pollen can survive for the better part of a year in a strictly very low humidity environment. It takes at least 2-3 days to adequately dry pollen using a dessicator.
After that, I seal it into mini zip loc bags, squeezing out as much air as possible. Then I heat seal it in a mylar bag, also squeezing out as much air as possible.
I find that if I dry it well, then I don’t need to put silica in with the pollen in the bags. It would be better, but I do worry about it puncturing the bags if they go through mail rollers.
Store these in the freezer for longer term viability.