I started by just trying to make stuff out of paper. It was cumbersome and crappy but all you want is a basic pattern. If it looks like it fits, great. If not, trim it. If you need more paper, just tape it on and trim that any old way. You should see the patchwork mess that my patterns where but after that I traced them to 1/4" foam, for armour, made it slightly bigger because of how you loose a bit when pieces bend and curve. Hotglue = welding for foam
, then 1/2 water, 1/2 white glue mix in 4-8 layers depending how you want to piece to look with paint on it.