FFFF wish I'd seen this before.
For my May hat, I used a foamcore base, and covered it with orange fabric. It's.. kinda ghetto looking TBH LMAO but it works well enough. Use the squishy, fabric-y sort of foam, the kind that you find in bra inserts and shoulderpads, rather than craft foam. Think of it as being used like interfacing, only as a sculpted structure.
Roll up the ends that would go under your hair, try to make it as flat as possible. Then shape the sides that tape up to the front of the hat and meet up at the front. Then cover all of that with orange fabric, whatever you're using to make the dress.
For the skull, you can build it out of paperclay or crayola model magic.
Hope this helps you in time!
Klan Klang (Lovely Bomber) - Macross Frontier: SnT - (15%- Sewing and logistics)
Jam Kuradoberi - Guilty Gear - (95%- new wig+touchups)