This is where I got sneaky.http://xenonray.deviantart.com/art/Midna-Papercraft-Download-354703794
I use the papercraft download, blew up the helmet images to be 24" wide and printed them out. Then I cut to shape, taped the pieces together and used them as the template for my foam.
-Fatigue floor foam - http://www.amazon.com/We-Sell-Mats-Interlocking-Anti-Fatigue/dp/B001EJPGG4/ref=sr_1_1?ie=UTF8&qid=1381070190&sr=8-1&keywords=fatigue+floor+foam
you can get a set of 4 of these from Harbor Freight for about $10. I used 2 sets, I think.
-20 large sticks of hot glue $15
-Heat gun $20
-Soldering Iron $5
-X-acto knives (around 3 blades)
-Model Magic - http://www.amazon.com/Crayola-Model-Magic-Mylar-Pouch/dp/B00000J0SM/ref=pd_sim_t_2
- I think i used three 4 oz packs. - around $9-$12 at Michaels
-Floral craft wire, foam - http://www.amazon.com/Luster-Leaf-Rapiclip-Foam-835/dp/B0026WGDYW/ref=sr_1_1?ie=UTF8&qid=1381087602&sr=8-1&keywords=foam+wire
- one pack of this was more than enough. I had lots leftover.
-4 tones of grey spray paint, any type, really, but I used indoor/outdoor matte and metallic
-Silver metallic flake paint, or Silver Rub n' Buff would work too $4
-2/4 sheets of standard craft foam, color doesn't matter. .50 cents
-Black acrylic paint $3
-Mod Podge, matte $8
-Sealer/clear coat - $8
-High temp hot glue gun $15
The helmet is in 3 pieces - the front, slightly curved front piece - 3 layers thick, the bottom half of the crown, 2 layers thick, and the top half of the crown, another 3 layers thick.
I taped the blown up prints to the foam and cut them out, one layer at a time, making the bottom two slightly bigger than the front, since I knew curving it slightly would make for some distortion. Using the very hot glue gun, I quickly put down a base layer of steaming hot glue and pressed the middle layer of foam onto the first one. Because the high heat gun is so much hotter, it will stay liquid longer, and give you time to hold it in a curved shape. After a few minutes, it will form up and hold it's shape. It's only a very slight curve, remember.
Add the third in the same way, then cut off the excess material. Add more glue to the seams and use small clamps as you go, if desired. They aren't necessary, but they can help you work faster.
The crown I build oversized, so the inside is filled with foam padding. If you want something smaller, I would cut the main front printed out piece down to 18" and size down the crown accordingly.
Clamps will be more of a help for the round crown, as well as a large form such as a very thick pipe, to get it circular. you will have to work in stages, wrapping the cut pieces around the previous piece and holding in place while it cools. Fill cracks with more hot glue. If you have any particularly wide cracks, cut a small piece of craft foam and use that to bridge it. On both pieces of the crown, I staggered where the seaming occurred to give a better balance. I cut 2 pieces of foam the same, then cut my printout in half and retaped the previous ends together. The middle piece of foam seams in the front, while the outer pieces seam in the back. This whole assembly process make take a couple of days.
I kept the large print out as a template of where the lines go. Using a hot soldering iron or wood burning tool, I punched shallow holes where the lines go, then removed the printout and connected the lines. USE VENTILATION. AND A MASK.
The thick 'wires' are foam floral wire - it's thicker than the plain green regular wires, and covered in a tube of perfectly circular foam. This stuff will melt when exposed to high heat hot glue, so you can use regular hot glue to attach. The 'snakes' were made with model magic and allowed to dry. The giant 'eye' was made the same way. There are spirals of gently ascending craft foam built on more hot glue on the sides of the lower crown. Some of this part is guess work since the original game model doesn't have all that much dimension, but I knew I wanted it to have more than painted lines.
To save time and money, you are welcome to simply paint the lines rather than construct or melt them.
I started with an overall base layer of black acrylic paint, then dark grey, then random light gray, sprayed from a distance to add to the metallic effect. The snakes I used silver flake on, because they do stand out in graphics, along with the eye in front, and the eye in back.
Before painting, I dug the soldering iron into the bottom of the helmet in a few places to make the broken cracks.
After that, i dry brushed some extra silver flake paint here and there. and painted the burned lines in black. The inside is painted in black, as are some of the other edges around the raised craft foam, around the eyes, and under the rim.
The top 'bumps' of the crown aren't actually supposed to show above the top edge of the front piece, but I wasn't going to cut it apart by the time I realized it wasn't quite right.