I was faced with the same question on my last few runs. It is hard because so many people have their own way of doing things, and sometimes are stuck in their ways.
My secret for whenever I have a question about something that I am not sure on, or something that I hear many different opinions about... I go to
MonsterGardens.com
I stumbled on their videos a little over a year ago when I was inquiring about Gavitas, and they seemed to be the ones with the most "know-how" about the products. So I gave them a call, and they told me more information about the Gavita lighting, nutrients, climate control, and everything else that i could think of.
I asked them about this issue... Is it better to put your plants straight into flower (12/12) or give them a day in the dark?
They told me so many different ideas about what different people are doing at the transition period. The best advice came from Jeff there, and he told me that he actually feeds his plants with Big Up Powder (Humboldt Nutrients) about 5 days before "the flip over," and then puts them in the dark for 48 hours. He said that this helps to trigger them into the flower stage a bit quicker, and that the pistols will come out about a week earlier.
I tried this out, and it did just what they said it would do.
Big up for 5 days, dark for 2, and then 12/12 from there forward.
I hope this helped you out, MG helped me out big time, so I thought I would pass on my "
secret information source" to you.