From experience, I can tell you that it is not only WHAT you put into your compost that matters, it is also HOW. You can't simply pile your heap with nothing but grass clippings! I had 7 compost piles of grass clippings and all of them turned into a dry mouldy mess! The reason is that it chokes itself out. The pile needs a mixture of organic materials to promote a variety of bacteria. I also find that layering with ordinary dirt also helps encourage worms and other larger bugs to help with the break-down process. Turning the pile aerates it as you mentioned. GOOD LUCK!