yeah we have been using compressed air hits for years and years, i use a compressor personally. Will have my own tutorial up soon finally.
Check out my fake blood tutorial also for some hints

http://www.sickindividual.com/tipblood.html

mix red food die with milk

for intestines: Fill dialasis tubing with jelly and fake blood

the brain
 

to make the brain u can put a plum in the center of a boll of jello and skwirt red and blue food coloring gell all lover it