Flushing permissions cache?

I'm having alot of trouble getting permissions setup on xwiki. My biggest problem at the moment is that it appears the permissions are cached. Other than restarting the servlet container how can I flush the permissions cache? Also, how do these permissions work? I'm going through XWikiRightServiceImpl now to try to understand this. It looks like permissions are exception based, one it finds a matching right it just returns. Is there any way to setup something like cascading permissions?