Xman is right, stretching behind the grain is the best way to go. If you keep stretching every which way you will always feel a little stubble here and there it doesn't mean you have not gotten a good close shave.

I can shave with an electric razor and my neck which is my problem area too feels as smooth as a baby's bottom but five hours later I have a shadow. With a straight I can feel a little stubble but 12 hours later the stubble is no worse and there's no shadow.

With me I find to really get everything on my neck I have to shave straight across my neck. I can run my hand up and down my neck and its real smooth but run it sideways and yes there is a bit of stubble. I haven't found any practical way of shaving straight sideways across my neck with a typical straight without killing myself. I've tried varies angles and arcs and for me it just doesn't work. Now I have a traditional Japanese Straight which is half the length of a usual straight and I can do it with that. But quite honestly its not that important to me so I rarely bother. Also remember the more times you run the razor over your face to get that last micron of stubble the more you risk irritation. It turns into the law of diminishing returns.