I would make all things at high dynamesh then duplicate, and zremesh + projection, but as CheeseOnToast said there is no magic it should be ultra dense mesh!
Here you go with another tutorial (this one is for charakters): http://www.3dtotal.com/index_tutorial_detailed.php?id=1763#.VHrho8lSOF9 In the end I guess there isn't just one way to approach it. The thing is, before you start worring about this high poly to low poly workflows, you have to completely understand the basics…