Abstract: The present invention is directed to a method and heating and spraying apparatus utilized for regulating the temperature of highly viscous cold process coating material tht is sprayed by a single pump on a surface, such as a roof and the like. The heating apparatus includes a vat designed to hold a quantity of a heat transfer medium, such as oil. A burner provides a source of heat to the bottom, sides and ends of the tank or vat holding the heat transfer oil. Mounted within the vat is a serpentine configuration of serrated finned tubing. The serrated finned tubing provides the maximum heat transfer while maintaining a compact and portable size. The loops of the serrated finned coils are mounted unconstrained within the vat to permit any relative movement, such as that produced by thermal or pressure expansions. A thermostatically controlled fuel supply system automatically monitors the temperature of the oil transfer bath to regulate the temperature of the coating material.