Some hints I picked up from an expert on scupting dolls/babies/faires is

1-)  DO NOT use metal tools to sculpt with, they will re-act with chemicals in polymer and leave item with dirty spots, use wood or rubber instead on the part of the tool you use to scuplt with at least.

2-)  Make a wire armiature to fit inside the mold of your doll to add flexibility and strength to finished product.  It will aid in being able to pose your doll and then after curing add to strength of overall doll.  For very small dolls/babies/fairies only use a small gauge wire such as 20, no more.