Brake boil over

If there is still air in one of the systems, when you press the pedal, it compresses the air, when you release the brake, the compressed air can shoot a violent return to the master, blowing fluid past the caps/vents.
Set the emergency so the shoe springs can't return the shoes.
Have a friend pump the brakes a coupla times and hold the pedal down, remove the M/c caps, and have the pedal released.
If you have a fountain of fluid return, - that's likely air shooting fluid back.
That system needs more bleeding.
Rinse any brake fluid off the paint immediately, as fluid is excellent paint remover!