Brake emergency

fluid came out the back when I bled it. I think hoses are good. However I do see that the front rubber hoses are nicked up pretty good from hitting this little L shaped guard? not sure what that is for.
What does Polishing rust off shoes mean? All shoes were brand new. 1 rotor was brand new. the other 3 rotors looked ok. hit everything with that CRC brake cleaner stuff.

Anyone else have a problem with ordering wheel cylinders from Oreilly? Online said all 4 wheels use same cylinder. When in reality the front wheels actually take a different size altogether. That was a pain to track down.