The needle idea has merit but IMO anything over one needle is going to get way too complicated, and even with sharp needles any tool like that stands a good chance of compressing the fill material.
I'm thinking the points slide down the side of the barrel, with the tapers towards the centers, so they're, at worst, compressing it towards the middle.
A cartowashing machine certain sounds like a good idea and would no doubt be a ton of fun to design and build, but could ultimately cost far more than can be justified for cleaning a consumable item.
I don't think life would be any fun if I only did things that are practical.