I plan on making a Raiden mask soon, so if I get ahead on it I will post up some pictures and most likely a mini-tutorial as well. But until then, you will definitely need a cast of your own head to even begin building Raiden's mask. You can build and fit the pieces onto your own head, but it will be quite difficult. So if you have a friend, ask them to help do a cast of your head, which is a relatively simple simple process. All you would need to do is to build up many layers using plaster-bandages. Nevertheless, it would only cost about $20-30 (or less) to make a single durable cast out of plaster-bandages. Of course, the cast would be ever so slightly thicker than that of your own head shape by about a centimeter, but that's still better than building a mask from scratch without a base to work from. But that's it for now -- let's just say plastic and putty are yours and Raiden's friends.
**edit** I do apologizing if this is bumping up an old thread, but I'm merely posting for reference purposes in the hopes of limiting the thread build up of already existed topics.