For the body panels, do you think you could get some big blocks of foam then carve them with a knife a sandpaper and stuff. I think it might be a bit easier than trying to do it with wire.
I don't know how many people have seen Fantastic 4 rise of the Silver Surfer, but I watched a special feature on how they made the fantasticar. And they pretty much cnc'ed the panels into foam, then sprayed on some waterproofing stuff, then created a mould then casted the mould. Perhaps you you try something similar with hand rather than cnc.