You can cut a few branches an put them in a flower vase in a dark closet under a small flourescent light. Set the lamp on a timer for ten hours on, fourteen hours off, and make sure you don't interrupt the dark period with any light whatsoever. If you place the vase on a paper plate, it will catch some of the pollen and make less of a mess. When the flowers start to produce copious amounts of pollen, gently shake the stalks onto the paper plate. Be careful not to get the pollen wet, because you'll want to keep it very dry for short term storage. Once you have gathered the pollen on the paper plate, fold it gently like a taco, and dump the pollen into a small Tupperware, or storage container of your choice. You can later use this pollen, and a small artist brush to "paint" a few flowers (buds) on your females, to produce some seeds for later. You don't want to keep inbreeding the same plants over and over, but once or twice is usually okay.