With a ching sling I did see a video in the internet on how to use it, and some good positons for a steady shot if you don't have anything to set it on.
I'll see if I can find the video again...
hmm didn't see the video did find a how to install it
http://www.shottist.com/use.htm
This picture shows someone using it...
http://www.gunaccessories.com/Galco/...ChingSling.asp
if you look closly you can see that the first strap goes behind his bicep so you can put backward pressure while holding the rifle which should allow you to steady it more ...
Sorry but that's all I could find...