What is the exact dialogue a crop duster pilot will have, if any, with ATC on a routine flight?
In most areas in the U.S., none. As the flights would mostly take place in Class G airspace.
Class G airspace is typically the airspace very near the ground (1,200 feet or less).
Radio communication is not required in class G airspace, even for IFR operations. Class G is completely uncontrolled.