I too use the soldering iron sealing method. Also pressure test the tank along with your fuel and pressure line attached. The easiest method is to pressureize it, pinch the lines, and submerge the assembly under water. Air bubbles will escape at the location of the leak.
The repair is a temporary solution, and will suffice until you can install a new tank. Pressure test your new tank also.
"Yellow Jacket" Mugen MTX-6, Picco Torque
TeamNITRO RC Club, Lynwood, Illinois