You can use this picture to make your own cosplay parts. Each element of the costume I am doing exactly as on the picture. Although I'm rarely using styrofoam. I need it only when the item is thick
1. Sketch the element with all details,
2. Cut the form of the polystyrene (Styrofoam XPS),
3. Cut all the elements of the EVA foam and stick it on the polystyrene (for gluing I'm using hot glue),
4. Paint it on the right color (acrylic paint),
5. Add shadows and details.