There's an detailed report of a small manufacturer in Burundi here and in English here. The report talks to the company's founder, a buyer, and an investment adviser.
The company says that sells its products (sticks of chalk for schools) more cheaply than Chinese or Kenyan imports. It buys the raw material from these countries, and adds value in the preparation of the end product. As other developing countries become richer and specialise in production of higher value goods, their manufacturing of lower value goods is likely to become less competitive in the Great Lakes region (as their wage bill rises, for example), opening the door for local producers to move into production.