Nose putty is often needed to make lumps, creepy hands, etc. For a brown color add 2 teaspoons cocoa. Use latex or tempera paints to decorate as needed. If you plan to use sound effects in your skit, it is important to have access to a microphone. Check with the facility where you are holding your pack meetings.
Most rental stores carry karaoke sound machines.
Also, you can pre-record your sounds on an audio cassette and play them back when needed. Drop two pie pans taped together with metal jar lids inside. Hit a pan with a metal spoon. Pour rice on an upside down flat cake pan. Hit a half-gallon plastic milk jug on the end with a rubber spatula.