Take the female plant, move it somewhere away from any other plants and away from any fans/circulating air. Take a paint brush or your finger or a pipe cleaner and brush some pollen onto the bud. Leave it for 15 minutes or so, then take a spray bottle and lightly spritz the other buds. Label that bud/branch (I use a ziptie around it). Then return the plant to the grow room.
I would suggest doing an entire branch as opposed to a single bud.
For best results repeat every few days for two weeks.