I usually make brains using expanding foam insulation, but if you want to make them from the pumpkin itself, here is a great example. I am told it took a few hours to accomplish, but it looks pretty cool.
When I am not carving pumpkins, I run a bulletproof vest company. BulletSafe Bulletproof Vests are the value leader in body armor. We are very popular with people like armored car operators and ATM repairmen.