If you really want one, and can spend some time on it, 2-3 days worth,like 4-5 nights after school or work. Drying time is the biggest thing, make sure it's dry before going on to the next steps. You can use so many different types of materials, cheesecloth, burlap, paper towels, the cheaper the better w/no design or coloring. I know it sounds funny but, used fabric softener dryer sheets almost anything. We use a combination of several things for glues and fillers, depending on what we are trying to achieve. Latex, Monster Mud, Great Stuff foam, liquid nails, spray adhesive.
You need a skeleton, or skeletal frame, we use what are called "Bluckys" which you can get at places like Big Lots and on-line, they are usually under $10.00. You can go high end and use a "Bucky" skeleton, but for a 4th quality your looking at around $80.00 to $100.00. If you can afford that just by one already done and save yourself the trouble.
I'll include a link to a good method, Deathlord is the master with props.
If nothing else try it, you won't be out much and you might find a new hobby. If nothing else bury it in the woods or along the roadside somewhere and wait for the news report.
http://www.deathlord.net/RottingCorpse/corpse1.htm