Mixing fine materials with coarser pieces will help maintain an optimum environment for the microbes. We don't have to buy them. Mother Nature gives them to us at no expense. Microbial action is slow but we can help it provide an environment to encourage more rapid decomposition. Since what microbes need to work is moisture and oxygen, composting equipment is always designed to make both available to all the material in the pile.
Manufactured units are available that make turning the pile and aerating it quick and easy.
Most are effective and easy to operate but they may be costly. This is the type of composter that Athens-Clarke County Recycling Division offers. He suggests a design made of discarded shipping pallets. One pallet is laid on the ground and four are wired together to form walls around it. Air movement from the bottom and sides brings oxygen into the pile.