I have had fun with the "stream machine" water gun. You dip the tip into a vat of pudding, cake batter, mayo, or other thick slime, then pull back to fill the gun. Stuff the tip down someone's shirt of pants and unload. Fills em up in a hurry. Comes in lots of different sizes, but the short ones are the easiest to handle and still hold a lot of sludge. Plus you can also shoot slop across the room with em and really make a big splattery mess.
Just google "stream machine water gun" and you'll see lots of choices.
They have something like this in Thailand for their Songkran water festival but on a bigger scale. They are banned as they are so powerful but there is a good blackmarket supply out there during Songkran ! They would work with Gunge but need the hole at the end enlarged to work well. We brought some back to use for this but never got around to doing a shoot. They will fire water a good 30 foot at quite a force so can't see gunge being a problem.
Love you, too
