Fiberglass Mannequin Costume

Hello all, first time poster so I hope I'm not doing something wrong but I'm making a mannequin costume and I figured I'd give build updates and get feedback. So my main focus is to have the glossy plastic look of plain mannequins in department stores but with a catch, my plan is to have the lower jaw detached from the upper section of the mask so when i open my mouth the face appears to crack and break like some silent hill monstrosity or something. My official plan as of now is to buy a plain white mask from a party store, along with a bald cap and some white nylon and put all of them on accordingly with the nylon stretched over and have someone paint over the sections with bald cap and mask with some sort of adhesive (i'm thinking modpodge but unsure if it'll keep the nylon in its stretched position), being super careful not to glue myself in it, and (hopefully) remove it all to have a semi cohesive piece that retains its shape well enough that i can inflate a balloon in it or stuff it with something so that i may coat it in fiber glass on the inside for rigidity. once the mask is cured ill cut off remaining nylon and separate the jaw section. Then Ill glue either elastic straps or black spandex or nylon to the inside which will pull the mouth shut (I predict I'll need to thicken the area of contact between the jaw and face on the lips to have more space to contact so they dont overlap), and i may use more white nylon for the neck and ears area. So I'm looking for any advice someone may have if they have the time and wish to spread some knowledge. I'm working on a serious budget.

Side project: bendable "doll" hands, the same idea as above a hard plastic shell except these would be sections glued to black gloves to look mannequin like but still have full range of movement. Current experimental theory: could i paint polyester resin on gloves and cut the sections apart once cured?

Thanks anyone who takes the time, I've always loved the creations that come from artists that all refer to this forum so I'm curious if I sound like a total amateur in making/ designing/ Building XD