Poinsettia reflowering advice

I would like to try to get this poinsettia to reflower this year. After last Christmas it was a fairly poor looking thing. After cutting in right back and keeping it in the greenhouse it is now standing quite proud. I know it’s got to be kept in total darkness indoors and only out in the light for 6 to 8 hours a day. Before I start that process should I pinch out the growing tips or should I have done that earlier in the year? Any advice would be much appreciated.