Special starters or compost activators, along with weird mixtures of herbs and other sophistications, are often recommended to "improve" the quality of the finished compost product.
These compost activators include bacterial cultures containing strains that continue working at lower than normal temperatures. They have some value in speeding up decomposition during cool spring or fall weather.
Just as effective, however, if available, are bacteria-filled screenings from an old compost pile, well-rotted manure or soil from a rich field. If the only soil available for building a compost pile is a sandy loam, a commercial compost culture will speed breakdown. These should be cultures of bacteria, not herbal mixtures which claim to be compost activators.
There is no reason why the pile should have an offensive smell if properly covered with soil: a 4-inch layer of earth absorbs all odors. However, if blood, manures and other rich organic substances become a bit odoriferous, add a little extra superphosphate.
One caution should be given: do not add large amounts of fresh wood ashes to a compost pile as they form lye and can injure bacteria. Mix fresh ashes with a little damp soil and allow them to stand for a day or two, after which they can be used safely.