I'm new here, but I figured this is as good a place as any to ask about some techniques regarding making a Mando Cosplay.

I've already cast a helm from a design I made, but I need to stiffen it and get rid of the lumpy bits so as to create a smooth dome. (pic related)

neckst.

I want to make foam armour that's also layered with recycled PETE or PET (for extra gloss and durability).

Mando Mercs Costume Requirements:
http://mandalorianmercs.org/get-involved/costume-requirements/

Mando' Templates:
http://mandalorianmercs.org/get-involved/costume-templates/

feel free to add other cosplay/custom armor