I want to repot a poinsettia what type of compost should i use?

an ordinary potting compost should be OK, cut it well down, keep it outdoors during the summer, then in about September bring it indoors. I was told that it needs 13 hours total darkness a day for a couple of months to ensure that the bracts turn red, BUT I live in Spain, and we grow them outdoors all the time here, and mine turned a beautiful red just right for Christmas with out any special treatment.