On a car I was taught these steps. It takes two people. I cant tell you why this might work, I dont understand the workings of the brake cylinders. But this method would push the bubble in the opposite direction and involves "closing" and pressurizing the brakes.
1: One person pumps the brakes to pressurize the system.
2: With the brakes held, the second person opens the zerk and relieves the pressure, then immediately closes the zerk.
3: Release the brakes and add more fluid ass necessary
4: Repeat until the bubble is gone.