Most of us here on the forums build our armor out of eva foam. These are most accessible in the four pack of puzzle peice floor mats. The cheapest place to get them is usually harbor freight. Craft foam is too flexible and thin, but works great for adding layers and detail. Glues and adhesives are dependent on what you have available or are willing to work with. I hate hot glue as it gets all over the place, the seams arent great, and I burn myself, but I have also seen people make professional grade things with hot glue. I prefer contact cement as the seams will be very fine and it will be hard to tear away. Super glue and other adhesives will work fine. I highly reccomend watching videos by kamuicosplay, zonzonzombie, punishedprops, eviltedsmith, and any other you can find on youtube as this will give you a great idea on how tk work with this material. Also do any reading you can on the forums of build of this helmet or just foam helmets in general. If you have any questions please ask and post progress so we can help you and guide you