I use stable breeder pack genetics that I've tested in my garden to do my crosses, and I chemically induce the m>f transition.
I won't give away the whole process, but I chemically prevent the female plant from producing esther, it then cannot produce the estrogen it needs to form buds, the plant becomes stressed, and herms.
I run over 400 plants per year in my testing garden, and can say that unless the plants are exposed to temperatures over 100 for a significant period of time (days) they will not herm.
I'm doing a m>f transition on my Instagram now, just posted pics today, sterquiliniis.seeds is my name on there.