I have no experience doing this, but you should be able to keep the males separate and collect the pollen by placing a shot glass under the sacks just before they open, even tap them a bit or poke with tweezers to help it along. Only collect the pollen and remove any green plant matter that may fall into the shot glass.

Next once you have enough pollen you can get a small paint brush and "paint" the pollen onto some of the pistols. This way you do not even have to pollinate the whole plant, since a few pollinated flowers should produce enough seeds for you!

I am sure there is a way to store the pollen itself, but I am not aware of the procedure for that.