I run my males out in a small closet, put a bunch of tin foil around the base of the plant, like a dish, and catch way more pollen than I need.
Then Ill take my selected female, at about 3 weeks into flower, and Ill cover one small branch that I want to pollinate with a plastic baggie, and spray the whole plant down with water.
Then, remove the baggie, and with a cue-tip or paintbrush, lightly brush the pollen you collected on your selected branch.
Wait one min, then spray the whole plant with water, without the baggie this time. This will deactivate the remaining pollen, stopping unwanted pollination.
6 weeks or so later, and you should have one small branch seeded out. I get about 15-16 beans this way, using a small undercarriage nug.