Fill a container of water to body temperature and put the chicks in, make sure to keep their beaks outside of the water for air. After a couple of minutes, their body temperature will be up enough that you can stick them in a brooder and dry them with a blow dryer. Don't leave them alone until they are warm and dry.
I've saved chicks and baby goats that looked absolutely dead by the warm water method. (The warm water gets their body warm faster than any air method of warming.)