Well technically you can't "make hermies". Whether or not a plant herms naturally is a trait in the plants DNA. Using a spray to reverse a plant, is just that, reversing it. It is not a herms issue at all. You can force ac plant to herm as Dank mentioned, but that is still introducing something to the environment to force the male sacs to form. It's not the natural herm trait showing itself. Annnndd, I say all that, to say this, lol. There are a bunch of reversal sprays on the market now that growing is becoming legal in more places. Some are all natural, some aren't. I'm sure it will work, as the process of reversing isn't all that complex. But I personally don't trust the sprays enough to use any of the plant material once it's been sprayed. I trash any plant I reverse. So if I plan to reverse a strain, I just grow it in a solo cup or something, or take a cut and reverse it, rather than waste a big ole plant.