I covered the bottle with silver foil tape, then clingfilm.
I have started the layers of fibreglass. It is not an easy shape to build.
To get the bottle to stand upside down, I core drilled a hole in a short piece of 7" x 2" I had lying around, so the bottle stays exactly still upside down.
I am waiting for the bottom to set before starting on the sides very soon.
Messy business.