UnOrthodOx (I think I spelled that right) had some pretty sweet tutorials on reproducing skulls. You might try to look up some of his stuff.
Oh, it will stick together once dry. If it were me, I'ld make a plaster 2 piece mold (a lot cheaper to possibly ruin a plaster mold than a latex/silicone one) to pour that into. Just coat with vaseline to keep that mache from sticking to the sides.I tried the paper machie route which was cheap enough but took a LONG time to make one.....I don't have a budget (laid off) so I thought about making a mold to try the paper machie paste (paper,water,flour in blender) and pour that in a mold....Not sure how that would work or if it would even stick together....ZR