A method and system for coating the internal surfaces of a workpiece is presented. A bias voltage is connected to a workpiece, which functions as a cathode. A gas source and a vacuum source are coupled to each opening through a flow control system. The flow control system is capable of a first mode which enables a first opening to function as a gas inlet and a second opening to function as a vacuum exhaust. The flow control system also has a second mode which enables a first opening to function as a vacuum exhaust and a second opening to function as a gas inlet. The cycling may also be used to coat internal surfaces of a workpiece with a single opening. Cycling the flow control system between the first mode and second mode is performed until a uniform coating along the internal surfaces of the workpiece is achieved.