Here's the basics for EVA foam armor fabrication, any techniques used in this tutorial can be modified and applied to any suit of "armor"
EVA Foam Floor Mats
3mm and 6mm Craft Foam Sheets (any color)
Razor Blades (a lot of them, foam dulls blades fast)
Hot Glue Sticks and Glue Gun
Nylon Webbing and Elastic Strapping (thickness varies on project)
Plasti-dip (any color)
Acrylic paints (color varies by project)
Step 1: Reference/Patterning
For this build I collected as much reference as I could, from all points of view. After that I sketched out the shapes of each individual parts of the armor, paying close attention to the scale and constantly checking for sizing. A great tool for this process was having my somewhat large monitor, this allowed me to inflate the pictures to scale, then trace the rough shapes that I needed. I've heard of people successfully doing this with projectors as well.
Another way to make patterns (the most precise/time consuming way) is to carve pink insulation foam into the desired shape, cover it in masking tape, then cut it away to make a pattern. I used this method on the bracers due to their funky shape.
Step 2: Cutting Foam/Main Assembly
Now that the armor is all patterned out, it's time to get cutting. This can be simply done by tracing the patterns onto the smooth side of the foam floormats (it tends to have two sides, one textured, one smooth). Then cutting them with a razor blade/box cutter, the trick to clean cuts is to use a sharp blade and to cut at a 45 degree angle smoothly and slowly. If you happen to mess up foam is pretty cheap to replace, but you can also sand foam, just work your way up to a 200-300 grit sandpaper.
The best way to approach a build is to think of it in layers, using various tidbits of that 3mm and 6mm craft foam you can build more and more detail. Flatter pieces and pieces that need to be laminated together can be glued with contact cement, and some smaller pieces can simply be hot glued in place.
Some pieces will need to be curved, the best way to achieve this is with a heat gun. For sharp corners I've found that cutting a trench in the foam, then filling said trench with hot glue and bending it works extremely well. On the snowtrooper I used these methods to create complex forms throughout the suit.
Lastly in fabrication, before you head to painting you'll need to "heat seal" the foam. Just wave a heat gun over the whole suit once, you'll observe a color change in the foam. This is the pores of the foam closing and creating a smoother surface, paint also adheres better to this surface, and it will hide some of your crimes from cutting/gluing.
Step 3: Sealing and Painting
When using EVA foam one typically adds a layer of sealant to protect the foam and give paint something to adhere to other than foam. In this case I used plasti-dip, a sprayable rubber meant for tool handles. On every piece of the suit I went over with 5 layers of plasti-dip, and I ended up using around 5 cans.
After sealing it's finally time for painting, I tend to use acrylics because they're cheap, but I know you can use oils and such. I try to stay away from spraypaints because I've been told they tend to crack. To paint this suit I started with a basecoat of white, then used grey and red for the various detail pieces on the armor. After that, I used two or three "washes" of black to weather the armor and make it appear battle-worn. To apply a wash just use watered-down acrylics, paint it on, then wipe/dab it off of the surface. This leaves behind staining that makes it appear that it's been around for a bit. I also used a technique called dry brushing to make scorch marks on the bracer, there was an ugly seam that I wanted to hide and that's the best way to do it. To dry brush I just took a brush, dipped it into black paint, then wiped most of the paint off of the brush, I then dabbed the paint onto the area in various layers to get a more scattered pattern.
Step 4: Strapping/Finishing
To strap the armor to the wearer I used a series of velcro, nylon webbing, and elastic to attach the armor. Nothing fancy, all just hot glued to the back side of the armor. I used and excessive amount of hot glue here just to be sure everything stayed as it should.
This armor also had some cloth parts, these were just hot glued on!
That's it folks! I hope that this tutorial was helpful as a general overview of foam armor making!