Hi again, and thanks for your reply with additional information.
I just researched this for you, while awaiting your reply, and now knowing the fake milk will be spilled on a real fur coat, plus considering the church services, I don't know how these will work, but they're all worth a try:
Very watered down white Elmer's glue (water/glue mixtures are used to simulate milk in dry cereal TV commercials and some print ads). While it will be a little 'sticky', it's non-toxic, washable, and if the clothes are pre-soaked and/or washed right away, there should be no staining. (I actually don't know how you will get anything out of a real fur coat)
Coffeemate powder, mixed with water....it's non-dairy, but will make a white emulsion. Might have a slight smell to it, but shouldn't be too hard to eradicate.
White tempera paint (non-toxic [finger] paints used by children) mixed with water might work, and it should wash out of the actors' clothes easily, if they are washed immediately. Also, if clothing is sprayed with Scotchguard or other 'stain resistant' treatment proper for clothing, before, it shouldn't 'stick' too much.
Instant mashed potato flakes, very watered down--unless this will look to 'piecey', but you can run it through a blender/food processor. However, potatoes are very starchy (gluey?) Speaking of 'starch', you could also try powdered white starch, very watered down.
I think you'll find this interesting: http://tvtropes.org/pmwiki/pmwiki.php/Main/FakeFoodI wish you much good luck, and please let me know how everything goes and what you end up using.
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Edited by Cher on 4/28/2010 at 2:23 AM EST