The blue pigmented material ( I think was liquid latex which requires a catalyst to `activate') was the stuff peeled away from the finished mould of vaders helmet. Moving backwards from this, the blue stuff was encased in a fibreglass mould to maintain the shape during the curing process.
To create a mould of your helmet would require painting or smothering the helmet in the liquid latex, The blue colour of the latex is not necessarily an indication of a particular brand or product as we add a few drops of pigment ( paint) to ensure a proper mix with the catylist. Sorry for the long winded explanation. The liquid latex lined moulds are great for multiple copies without damage to the mould surface. When they show the creation of Vaders helmet you can see them painting the `gel-coat' directly to the latex mould, then the fibreglass matting or finer sheets can then be layed inside.
After they remove every thing from the mould you also see them flop the blue latex thing on top of a `helmet stand', with this latex mould technique this stand could even be the original carving from which the mould was made.Ive taken moulds from some really odd stuff, leather sand paper, tree bark. I have found liquid latex to be extremely co-operative to removal from even rough surfaces without any release agents being applied to the moulded article.
I hope the info here is helpful, I also hope it is all correct.
My background is in composite racecar seats, kevlar/ carbon, plastics and now leathers (in restoration). Any questions or corrections very welcome.