How exactly would one go about creating a lifesize plastic dummy/mannequin?

This is for a story I’m writing. A guy who owns a shop is also a craftsman in his spare time, and he creates a custom mannequin for the store-window. I want to accurately describe the physical steps he goes through in creating the dummy - casting it or molding it out of resin, plastic, whatever you do to custom-mold a dummy.

I’m hoping for a decent amount of information here, since I want to begin working on the story when I’m done watching the Giants game. So tell me all you know, craftsmen.

Depends on what he makes it out of. I assume he would use the material he’s most familliar with.
Some of these links may be helpful.

http://archive.amol.org.au/recollections/2/1/14.htm
http://www.costumes.org/classes/254pages/projects/dressformsdisplay.htm

http://www.instructables.com/tag/?q=lifecasting&limit%3Atype%3Aid=on&type%3Aid=on&type%3Auser=on&type%3Acomment=on&type%3Agroup=on&type%3AforumTopic=on&sort=none

There are these things called a Real sex doll? “Lars and the Real Girl” has one, I think.

Nothing like that, just a simple male torso, arms and head (not even a lower half) made by a jewelry-store owner for the purposes of displaying watches in his window.

I think I’m just going to have him carve it out of wood.

I just went to look at the Real Doll website. Definitely “uncanny valley” territory.

Is your character a good sculptor?

Nowadays, He would cast his mold out of latex or alginate of a model. You wrap the soft molds with plaster for support, then would pour in a casting resin to make the positives. Connect the pieces with epoxy and sand all joints and seams. Prime, paint and hair and eyeball.

A custom mannequin as specified in the OP created as an exercise in craftsmanship would likely be carved from laminated wood.

Or possibly constructed as fiberglass layered over a wire or foam frame.

Why would a jeweler want a mannequin to display watches? For advertising, perhaps, but all of the jewelry and watch stores around here just display the watch itself in the front window.

Not meaning to be difficult, but displaying a watch on anything other than one of those velvet or lucite pedestals is somewhat unusual.