For anyone who might be interested, Kink.com had (has) a video that is a tutorial on fisting done by a lady that goes by Princess Donna. The page seems to have been long gone, but thanks to the miracle of archive.org (and Kink.com not actually removing the video), it can be viewed
here. It is fairly informative and is not done to be porn, but completely instructional. I think anyone here who is into or is looking at getting into fisting will find it useful. If the link dies, let me know, I have the video downloaded and can upload it to my own hosting space if need be.