Google lizard landscapes. You'll be hard pressed to find a better list of tutorials on the net. There is more then one way to make a grout structure, but his videos will get you started. Only suggestion I can make on top of his method, is to play around with mixing sanded and non-sanded grout. Sanded grout is harder to work with and spread smooth, but its much stronger and has more texture. Non-sanded thins down much more, takes color better, and is easier to work with and apply. I just don't think its stong enough for the last couple of coats...and it has a tendency to crack if you put it on too thick.
Also, the loctite power grab self dispensing tube is REALLY nice...easy to manipulate and that stuff sticks really well and really fast.