I usually grow only regs, just because I've been doin it for many years. Back in the day regs was all there was. I germ seed then put them under 18/6 (T-5's) for 3-4 weeks. Then switch to 12/12 until I can see any pistils or stamens. I am very thorough with this step, using a loop to see better. Males are usually first to show. They are tossed, and females are put back under 18/6 for a few weeks . The key is to catch the reproductive growth EARLY, so the plant doesn't have time to fully start flowering. This whole process takes about 5-6 weeks so plan accordingly.  Happy sexing