A method of unloading and producing liquids from a well uses a plurality of gas injection valves installed on a production tubing. The injection valves are controlled by pressure signals transmitted through a single fluid control line. A first pressure signal is applied to the control line to open the plurality of injection valves. Gas is pumped into the annulus at an injection pressure until a first pressure drop occurs in the injection pressure, the first pressure drop being indicative of gas flowing through a first, upper one of the injection valves. Pumping of gas is continued until a second pressure drop occurs in the injection pressure, the second pressure drop being indicative of gas flowing through a second, lower one of the injection valves. A second, lower pressure signal then is applied to close the first injection valve while leaving the second injection valve open.