The mix is basically the original stan's formula, before he started packaging and selling it himself. For one fat-tire tube it's just a heaping tablespoon (about 20ml) of mold builder (liquid latex, which can be acquired from any arts & crafts shop) thoroughly mixed with 1/4 cup of water. Use a 50/50 mix of water and auto coolant in there if you ride in freezing conditions. I use a polycarbonate syringe with a metal needle, which you can get at a chemistry supply store or almost any kitchen supply store or large grocery store, to inject the sealant. It will be called a basting syringe at grocery and kitchen supply stores. I think my syringe has 50ml capacity, the mixture makes 2 syringes worth of sealant. The sealant must be thoroughly mixed or the latex will clog the needle. I load the syringe by sucking the sealant up through the needle, don't try to load it by taking the plunger out, that will just make a big mess.
If I already have a flat, I find the hole and inject the sealant through the hole. If not, I inject the sealant through the tread side of the tube (not the rim side) so it will seal up immediately. Just punch the needle through the tube and inject the sealant, but be careful not to tear the hole when you stick the needle in the second time. The sealant will plug a big hole, but only after it has been properly installed and inflated. Also, make sure your valve is closed if you are working with a presta tube. Thoroughly clean the syringe ASAP or it will clog and be difficult to clean.
Install the tube in the tire and mount the wheel. Do not pre-inflate the tube before installation. Once mounted, give the wheel a slow spin to spread the sealant. Inflate the tire to your desired pressure, then give the wheel a fast spin. I use the crank to spin the wheel up to speed and then just let it spin itself out. This will thoroughly spread the sealant. Once the wheel has stopped, listen for leaking air. If you hear air leaking out, just turn the wheel slowly until you hear the noise stop.
What I've learned so far:
The sealant doesn't last forever, but I've been using the system for about 6 months and haven't needed to reseal a tube yet.
The sealant will seal BIG pinchflats, which is cool, but the sealant doesn't provide much structural strength. I learned this last week when I pinched the tube right by an older, very large snakebite and the tube split along its circumference. That made a very nasty mess.
You shouldn't use this sealant with continental tubes or any other tube made of natural rubber, the ammonia in the mold builder will cause the tube to decay.
Do not fill the tire with the valve at the 12:00 or 6:00 position, you'll end up with a whole lot of sealant in the valve and pump. I find that filling the tubes with the valve at 4:00 or 6:00 leads to minimal leakage through the valve.
I hope that helps. I know that's lotsa words, but it is a very simple procedure. It takes me less time to put sealant in a tube than it does to patch a tube. I can try to take some pictures if anyone thinks it is necessary.
Edited to add: I've done this primarily with Salsa 29er tubes, which don't have much talc in them, and some no-name 26" tubes that do have a whole lotta talc in them. The sealent still works with talc, but not as well.