Some 35 years ago I trained with an older artist who had learned the process of making papier-mache manniquins at one of the last of the display companies still using papier-mache. I try to continue in this traditional method, but it can be difficult to source the materials. Here, in brief, the practice, materials, and problems.
     Plaster molds are used. There are a few special adaptations for the production of papier-mache such as sealing the molds with shellack, and preparing them with a parting agent made from paraffin and kerosene.
     The adhesive is dextrine paste. It will not mold, does not attract insects, and it will not introduce lumps into the casting. Not as easily available as it once was, but still used as a food-packaging adhesive. I purchase it from an adhesive distributer, but there is a retail brand in the US called "Yes" paste.
      The papers used were known as "card-middle" and "red-flex". Both papers used to be available in a number of weights, up to .034 caliper. The selection of papers would be based on the size and detail of the casting. The first layer in the mold would be the thinnest paper. Alternate layers of gray, red, gray were used. The color difference helped to insure a consistent thickness in the casting, a very important consideration that contributes to overall strength and smoothness.
       Card-middle and red-flex papers were  also used in the manufacture of playing cards and books. Unfortunately the composition of these papers has changed in recent years, they now contain additives such as latex and polyester & are no longer useable for papier-mache.  I recently used the last of my old stock papers & and I am now searching for substitutes.
       Casein paint was the preferred finish, after the casting had been sanded and sealed with shellack.  When I began making papier-mache there were 3 brands of casein available. Now there are no real casein paints on the market in the US. There is only the Rosco Iddings "Casein" which uses a soy binder. It is useable, but takes a lot longer to build up a good finish, requiring  a shellack seal between coats.
       If any one has suggestions for soft-milled, non-sized, heavy weight papers, please let me know. 
         Some of my work is online at http://jimseffens.com