That's what I end up doing, actually. It's easier to work with a thinner piece of material, then transfer that to a thicker 'permanent' piece. Even if I'm not necessarily going to build a body shape again (how many longhorns do you need, right?), I'll usually have pickup or control cavity routes on there that can be re-used.
I do pretty much the same thing. I didn't do it on a build that I eventually scrapped and i took a look at where i could have used templates and realized that while they take time to make properly, they're almost guaranteed to save you time in the long run of your build - less mistakes, smoother transitions..... I just find that templates make your work cleaner and more efficient.
That being said, for neck pockets - i'm a fan of the rail method, but I whipped up the neck pocket jig from the tutorial section. (good way to contradict myself!)