plant hermaphroditic genetic offspring...
that is the only real way to greatly increase your chance of hermies...
light stress by messing with the plant's avg dark period by throwing in random light here and there... will for all intensive purposes just cause it to reveg 9.99999 times out of 10...
1.) surround the female with a bunch of males, then as the males start to flower and before they release their pollen take them away from the female... at the last possible chance without letting them pollinate...
2.) while still in flowering... give it LONG additional and random dark periods... like throw it in the dark for several days, then give it 12 hours light then normal 12/12 then back into a few days of complete darkness... etc... until desired result is achieved...