Hi All Newbie here

Some advice please on where i go from here. I have 4 plants approx all the same height about 18 inches. All of these were infected with spider mites when given to me at 6 inches. I now managed to free the all of this darn bug. I had to take alot of the leaves off of them because they were damaged. 2 of these plants are now ready to as their folage has really come back and are I assume ready to flower. But this is where i get confused because i have read so many conflicting ways on here on what to do at this stage. I've grown these plants on my window sill. At present it has been really hot so i have been putting them in the garden during the day and bringing them in at night when it cools, back to their resting place on the window sill.
For the last couple of days i have been putting one plant under the stairs in darkness for 12 hours then it comes out to join the rest of his/her friends. I thought i would do this one by one so i could sex the plants. Is this okay? From what I've read within 10 days I should find out if its male or female. If it was female I was going to take a cutting from this. Is this the right stage to do this? Also how long do i keep up with the 12 on and 12 off for? Any advice on where to go from here would be appreciated. I'm not using any lights unless its sunlight. Feed is tomato plant food. And plenty of TLC. Dont want to go into growing big time just want a constant supply of the smoking stuff. They are growing okay doing it the natural way i am and would like to keep it going like this. This is the first time I have grown this stuff so please keep it simple please. I've never heard of some of the things you guys are talking about is this because i am in the UK and many of these products are available in other countries?
Any help from here on would be appreciated. Many Thanks

Terroricia