"The Great Northern developed a large spreader, which it called a snow dozer. The spreader blade height was adjustable." J. C. La Rue, Jr.

Per DOCTOR REYNOLDS (doctorwwr@REMOVExxTHISyahoo.com), one operator can run a spreader in a pinch, but I always had two on the spreader. We often had the section foreman from Lacolle operating the front plow on the NJ, because he knew best where all the obstructions were. They were all marked with flanger signs, but the consequences of a missing sign were considerable.
We never opened the wing when plowing snow at speed. The wings are not very responsive, so we would set the wing in position while stopped, and then push the spreader for as long as its position was good. If it needed repositioning, we would stop and reset it. The wings were mostly used to clear sidings or to open up the approaches to highway crossings. The air-operated spreaders (newer ones are hydraulic) had a system of locks and cylinders on the wings. Only the front plow was directly operated by the air cylinder, from lower stop to upper stop.
To move a wing, you first stepped on a pedal to release the lock for the desired movement, and then moved the air valve lever to operate the movement cylinder to wherever you wanted it. Then you released the lock pedal and the lock secured the wing in position. The locks were air operated, too, just a plunger in or out that dropped into a hole or onto a rack. So it was not an instantaneous operation, and when the wing was loaded only the lock held it in position. Normally, when you are winging with a spreader, especially with only one operator, only one wing is extended at a time. Sometimes you have to make two or three cuts to avoid slewing the spreader and derailing it. It takes someone who really knows what he (or she) is doing. The wings on Russel plows, etc, are directly air operated, and they can be extended or retracted on the fly, as can the flanger blades amidships.