You don't really micromanage things, just like managers in a company shouldn't micromanage things. You don't make decisions on how much bread should be made by each of the 300 bakeries; you decide that making bread itself is important so you give subsidies. You decide that making bread locally is important so subsidies are only available to locally made and not imported bread. You decide that whole wheat bread is more important than white bread so you give subsidies only to whole wheat bread.