Abstract: As apparatus for and method of pneumatically reciprocating spraying means linearly between two end points with a minimum or negligible amount of lag or return time at either end point which includes an oscillating piston inside a cylinder member, said piston having an outwardly extending arm responsive to the movement of said piston to which a spraying means is rigidly attached. An air logic control circuitry controls and directs regulated pressurized air to and from opposite ends of the cylinder, each end receiving and exhausting different pressures of air at different times and in different amounts so as to cause the piston to oscillate in response to the differing air pressures at its opposite sides. Lag or return time is minimized by sensing when the piston is approaching an end point and introducing higher pressure air in front of the piston while at the same time dumping or exhausting pressurized air behind the piston to cause its immediate return.