Resin is uber expensive. I would say Model Magic, because it's honestly your best friend. But only for smaller props. It dries really fast, and with something like VV's headset thing, you want a little more time (though the stuff it cheap, sandable, and paintable).

Buuuut, if you want to maximize efficiency and reduce costs, make yourself a wife frame underneath. Wire a skeleton, then cover it with a sort of wire mesh. After that, cover it with aluminum foil to stop the clay/model magic/Fimo/Sculpy from groing throguh the wire mesh holes. Then quickly cover it with whatever you want to use on the top. ^^

Hope that helps. :3 Good luck!