Presented herein are a system and method (i.e., utilities) for monitoring the flow of materials used to mark road surfaces and other surfaces. The utilities utilize one or more pressure sensors to monitor in-line pressure of road marking material to determine the amount of material being applied. Electronic equipment receives signals from the pressure sensors, temperature sensors and/or additional monitoring equipment to generate an output indicative of an amount of material flow. In a further arrangement, the equipment generates an output indicative of a thickness of the read marking material as applied to a surface.