It is possible to cross your favorite two female plants to create a new strain of seeds that will produce all female plants. Preferably, these two plants will be different types of plants, not from the same mothers seeds.
This will create the best offspring, since it will not lead to inbreeding. It is easier to gauge the quality of female plants than male plants, since the smoke is more potent and easier to judge it is finer qualities. Plants from seeds created in this fashion will be all female plants since there will be no chance of male chromosomes from female parents.
Use Gibberellic Acid on one branch of a female plant to induce male flowers. Gibberellic Acid is sold by nursery supply houses for plant breeding and hybridizing. Spray the plant once every day for 10 days with 100 ppm gibberellic acid. When the male flowers form, pollinate the flowers of your other target female plant you have selected. Just pollinate one branch unless you want lots of seeds!
Once the branch has male flowers, cut the branch and root it in water, with glass under it to catch the male pollen when it drops. Use a rooting solution similar to the above cloning solution.Collect the pollen with a plastic bag over the branch and shake it. Use a razor blade to scrap up fallen pollen and add it to the bag too.
It is also possible to pollinate the flowers of the plant you create the male flowers on, crossing it with itself. This is used to preserve a special plants characteristics. Cloning will also preserve the plants characteristics, but will not allow you to store seeds for use later. Crossing a plant with itself can lead to inbreeding problems, so it may not be the optimum solution in many cases.
I once tried using Gibberellic Acid, sprayed on a healthy female, every day for over a week. No male flowers appeared on the plant. Your mileage may vary.