I know a few guys who will be perfect volunteers for your project if you like hehe
Not including myself, as I stopped that kind of thing many years ago, when aunty Bessy walked in on me one day, "god the trauma"!!
There are variety of churning devices. I remember a wooden one, like a thin, covered barrel.
This is what my mother-in-law uses and it has a type of wooden slat inside, which she turns and then somehow the butter in formed on the sides.
When's the big day mate??