big screwdriver and adjustable wrench
stick screwdriver tip in gas screw. take adjustable wrench and tighten it on the square shaft of the large screwdriver. push down on screwdriver handle with one hand while siumlatenously turning the screwdriver shaft counterclockwise with the adjustable wrench with other hand.
I actually have an old beat up op-rod that I filed the actuator handle/tip down to fit the slot which works great and has plenty of leverage. The secret is to never torque a gas screw in harder than firm hand pressure.