NOTE: Before a plant is chosen to be sprayed, you need to do everything in your power to force it to hermie through regular stress. Light stress. Physical damage. Anything and everything you can think of.... It defeats the purpose if the plant you spray was going to hermie anyway.
I like the colloidal silver method, because it doesn't involve caustic chemicals, and can make thousands upon thousands of seeds for $10. No Bull. There are many, many threads detailing how to do it, so I'll just give you a quick run-down of the steps.
1) Buy a couple feet of pure silver wire.
2) Buy distilled water.
3) Put two pieces of silver wire in a glass cup of distilled water, run an electric current through it.
4) Spray a female plant with said colloid, and repeat until male flowers start poppin'.
5) Pollinate a second female plant till your heart's content...
P.S.... Please don't do this to a strain that you are not familiar with. The only thing worse than male plants are hermie plants.