I am doing this right now for the first time. Colloidal silver is the best method, you don't want to stress the plant because you will increase the odds of the hermaphrodite gene being expressed in future generations. Just spray with a CS starting about a week before flower. Spray everyday once or twice until about week 2 of flower and you should start seeing many pollen sacs. All the CS does is change the chemicals in the plant forcing it to make pods instead of pistils, much lower stress... It is best to start the plants being sprayed on 12/12 at least a week before the plants that will be pollinated.
There are more details but they can be found with a quick search of the site.
You can "over flower" as well but the seeds will not have time to develop on the same plant. You would need to pollinate another plant that is earlier in flower.
Use at least 40ppm CS. I made my own very easily, there are many DIY threads for it here.