Paper mache is my favorite medium too, and I love Stolloween's site and info. I make mine over beach balls for an easy, reusable, deflatable basic shape. Then add the details over the top.
Once you get some shapes you like, you can replicate it with with packing tape, to get several pumpkin bases to mache fairly quickly. I did this making the skulls for the $20 prop contest.
Scroll down to post 6 & 7 and it shows the technique.