You can secure the mounting flange of the
Brake Master Cylinder in a bench vise, remove the master cylinder reservoir cap and diaphragm, install suitable fittings, install transparent hoses to the fittings, fill the master cylinder reservoir to at least the halfway point, ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully submerged in the brake fluid, depress and release the primary piston, continue to depress and release the primary piston, remove the transparent hoses, install the master cylinder reservoir cap and diaphragm, remove the fittings with the transparent hoses and remove the master cylinder from the vise.