How to keep a constant speed

[Brakie]

I watch former steam locomotive engineers open the throttle to notch five while switching and once he gets moving he would close the throttle and let the engine "drift" and if more power was needed he would use notch two or three till he reach the speed he needed then he would close the throttle and "drift"..

I was always amazed at the way these guys could manipulate the throttle and brake.