Putting the throttle just below idle detent is the way I was taught, and the way I've always done it. If the battery dies on you during the start, and you're above the idle detent, you'll melt the engine, because you can't close the throttle. I've always opened the throttle full open, back to idle, check where that is, close the throttle, and then initiate the start, and at 12% open it to just below where you saw it at idle. With experience, you can open the throttle there without even looking, doing it by feel. PT6s start very benignly, and the exact location of the throttle isn't critical, unless the battery dies. And 412 batteries have been known to die during start.