If you modify an existing plane, as I did, you can reduce the time somewhat, but it's not fast.

By CAD standards, the builder interface is clunky and tedious. So, I just start with a flyable plane, and gradually tweak it as time goes on, whenever I've got the patience. The data you can get makes it worth it at the end, in my opinion.

You can download the sim (PC and Mac) for free and try it out. It comes with several additional packages, "Plane Maker", "Airfoil Maker", and "World Maker", so you can design your own "stuff". ( http://www.x-plane.com ) and more info (including hundreds of downloadable planes) at http://www.x-plane.org/