Bench bleeding a master is super simple. Go to the auto parts store and get about 2 feet or so of METRIC brake line. Find one with 2 MALE ends that match the threads on your master cylinder. Remove the master cylinder from the truck and put it in a vice, keeping it level. Cut the new brake line in half. Screw each piece into the master cylinder. Bend each piece in a loop so they are fully submerged into the resivour. Fill the master a little more than half way full of clean brake fluid. Using a screwdriver, push in the piston in short, 1" or so strokes. Keep doing it until you get a good stream of brake fluid, no bubbles. Usually takes less than 2 minutes. I've tried other ways, and this is by far the fastest and easiest way. Then bleed the rest of the brake system. Try it the old fashioned way, by hand, not using the vacuum bleeder.