I used a electric controlled solenoid valve. Chief Stackable Solenoid & Manual Operated Circuit Selector Valves. It is controlled via a switch I mounted on the front bucket control valve. It is tied into the load/dump valve so when the button isn't pressed the loader valve works as normal, but when it is pressed the hydraulic flow from the loader dump/curl is transferred to the thumb. I used a 1/4 inch hydraulic quick disconnect fitting to cut the flow down to around 3 gpm. The thumb itself is home built.
