I have produced fem seeds using colloidal silver, I can answer any questions you have (pm me me if I don't check in here).
If you want to have more females from regular seeds, look here:
http://www.1stmarijuanagrowerspage.com/how-to-improve-female-male-ratio-of-cannabis-plant.html
I use Tiresias Mist, $20 on ebay. You can make your own. I am lazy and found the Tiresias Mist to work very well.
Basically, you want to start spraying one female a week before flower, twice a day.
Put the other females somewhere else in veg, put the sprayed plant in 12/12.
Continue spraying it for another 7-14 days, then put the other plants in the 12/12 room.
The spray stunts the plant. The extra two weeks make up for the stunt and also give the pollen sacks a head start so they are ready when the buds are ready.
When the pollen sacks start to get big, you can move the plant somewhere else. Then you can selectively pollinate the bottom branches of your other plants.
Pollinate the bottom branches so you can harvest the tops when they are ready and then let the lower ones continue to make fat seeds.
You will get fem seeds.
You may also want to look into preserving/freezing the pollen for later use.