Hi Killjoy and welcome to the site.
Your best bet would be posting some sort of introduction thread and then doing a lot of reading through the sites old posts. There is a section that is completely devoted to making helmets. Using the search function is your best bet. Try doing a search for "scratchbuilt helmet" and seeing what pops up. There are probably hundreds of threads with dozens of different methods and materials for making helmets.
Good Luck,
Jack