Zip tie a hose on to the bleeder. You want the hose the fit tight. Stick the other end into a container that has some brake fluid in it. Make sure the end of the tube is submerged in the fluid. This will keep air from entering the system. A plastic water bottle works well. Drill a hole thought the cap, run the tube through the hole and zip tie both sides so it is secure in the cap.
Open the valve and compress the pistons. I typically use a c clamp, or channel locks on an old brake pad. This will get any air out that might be trapped behind the piston. Close one valve. Install calipers on the spindle and bleed away. You can leave the valve open while bleeding. Bleed until you get clean fluid coming out. Close the valve on that brake and open on the other. Repeat bleeding. Make sure you don't run the master cylinder dry. As long as the hose is in the fluid and tight on the valve you don't have to worry about air getting
Close both valves and bleed normally. You should have good tight brakes.
f you still are not holding pressure you will want to look at rebuilding the master cylinder.
