Re: doing the double haul
Welcome to the forum,
If you look around in the threads in The Fly Cast, you can find some videos on this. Below is my own explanation.
I get the best line speed by giving a yank just after the power stroke begins. At the stops I shoot line to lengthen the cast and then repeat the stroke / yank until I have what I want out. Once I reach the terminus (distance wise) I let the remaining line shoot on the delivery cast. So, yes it can make a difference when you make the 'haul'.
That's how I do it, there are people who teach this who may not agree with what I do.