The nice thing about the Raven is that it's so cheap and crappy, you can just throw it away when it gets dirty and buy another one. It's the gun version of a paper plate.
However, if it has some sentimental value, like you saw it on COPS or something, refer to this webpage:
http://hometown.aol.com/jtjersey/Raven/raven.htm
Cleaning instructions are discussed.