Like Norton says, flextrack is more economical than the pre-shaped curves. I use a mixture, and one trick I use is to get a quarter circle of the pre-shaped, temporarily attach it, then trace around the ties. I then remove the curved track, and attach a piece of flex track to the attached straight portion of the main, and bend and fasten it alo g the trace marks.
I've had various degrees of success with this, and I have to be sure the bend is smooth, or I can get derailments even on 072. And I have to watch the inside rail and trim accordingly.