I am doing an EVA build at the moment. It is my second costume. Angelengend has some excellent tutorials on youtube to do a master chief costume. I found his methods easy to follow and he has links to the blueprints under his videos.
Sika product are great, as is Bunnings where I get my EVA foam from. Good start on the nose! I have a couple of those produce polystyrene cartons also. Made a Halo magnum out of one of them.
Then I got some Knauf XPS Climafoam from Bunnings and got better result due to the density of it. Free is...