Simple way to do body work is to Build the basic shape you want with plastic. If you can't buy any, use junk, spare plastic stollen from other kits. (Hobby Lobby should Have some sheets of plastic.) Use superglue to glue the plastic in place. Go to your local auto parts store. Get some Bondo or other two part car body putty. Mix it up, slap it on, wait till it dries, then sand it.
That is what I did on this one: