Instead of a kiln, any cheap handheld torch can fire vitreous enamel onto copper if you have a "tripod" to hold the copper so that you can fire the bottom of it with the powdered glass on top. Usually those sell for $40. These are instructions on how to show students in class how to make their own for free from coat hangers and a 6 inch square piece of plywood. One for every 4 or 5 students would be sufficient to keep the class busy firing vitreous enamel without waiting in line.
Torch firing adds creative possibilities not available in a kiln - firing parts of the piece hotter than others, applying fire momentarily to the front, etc. It also eliminates needing to warm up a kiln beforehand.