#1 Shaving cream. I'm not sure of your purposes, but a can will fill at least 3-4 pies up. It can also be used as a slime if you mix it well enough with water. It's also a soap based product so cleans relatively easily.
#2 Cake Mix. Do not try to create this on your own with flour based recipes. The store bought mixes are great and will not leave clumps in hair as standalone flour will do. Rinses off easily in shower.
#3 Pudding/Applesauce. Not much risk here. These clean up pretty easily on their own.
#4 Eggs, if you are into them, also clean up relatively easily.
#5 Food coloring - just use caution when using. Direct contact with skin will stain. High probability to stain white cloth clothing as well.
oatmeal really cheap but more difficult to clean up. Just oats, water and mix well. I just put most of the glop back into the container it came in for easier cleanup.
+1 for shaving cream. Insanely cheap, one can usually makes 3-4 decent sized pies and it's DESIGNED to wash away with water. Great coverage too, and you can squirt it into a bucket and make a half decent slime with it as well!
Love you, too
