You don't need to use smelly resin and fibreglass, you can use a whole host of other safer alternatives. Papier mache, bondo/epoxy, jesmonite, plaster bandage etc. Main thing to consider is the weight if you're going to wear it. I've used a papier mache like product called Sculptamold and it can be modelled a bit like clay. It can be air or oven dried, sets pretty hard and can be lightly sanded and drilled. Light as a feather and safe. You can get it from Amazon.
Use the search facility for more info.
If you do use resin/fibreglass make sure you have good ventilation, mask up and keep your skin covered to protect you from the really annoying itchy fibres.