I got this automically when going through the tournaments using John Stockton who's 3pt shooting stat is 9/10.
Ray Allen and Steph Curry are a 10/10 and probably Reggie Miller too I would have imagined. Whoever you use it will help to have the 3pt stat as high as possible.
Literally every possession I pass the ball to my 3pt shooter, do a crossover as soon as I get near half court to avoid any opposing defence. I prefer to try an shoot from the bottom of the court and from a standing still position.
When your ready press and hold X to elevate and release just before you reach the top of the jump.
When you have the release timing down you should be able to rain 3's using this method :)