Only recently I became aware that hypertufa could be used in creating large, natural appearing stones. Is there a specific "how to do it" type of article or website that could give explicit instructions on completing this process correctly the first time?
I wish to create a really large scale rock formation as the basis for a rock/cacti garden.
You're in the right place. Look through the titles of the threads and you should be able to find what you're looking for. There is a lot of good information here but you might have to read through several threads to find it all.
I think you need more concrete and possibly lime to make a "crete" that won't dissolve. The Garden Form.com also has a lot of information. Check out posts by Tango (he's no longer a member here - might be Tango88) - he does concrete that looks like wood.
If you Google "hypertufa" or "papercrete" you'll find lots of inforamtion. The best suggestion I can make is to do some small projects, keeping track of the mixes you use. You can leave a small thing in a bucket of water and see if it lasts without dissolving. If you look at the leaf threads you can get ideas for mixes and for great small projects.
Being a person who tends to start out big and then become discouraged when I run into problems I'm offering from my experience to start small. When you find something that works FOR YOU you can move up to bigger projects. Lots of people are working in concrete these days. My two cents worth is to suggest that you gather a lot of information, try out a few small projects and have fun learning what you can do with this stuff.