Some sellers, including giant First Student, will not release maintenance records for legal liability reasons.
Let's say you study the records and discover that they failed to perform a required task correctly
or on time. If your brother-in-law is a lawyer and doesn't have enough to do....
Chatting up the mechanic may work, though!
Like the man said: Do NOT touch the band that clamps the two halves of a "pot" together. Just replace
the entire two-pot unit. Two bolts, a clevis and two hoses.
And last I heard, it is not legal to splice a hose from the frame to a pot.
When in doubt, replace air brake components with brand new.
You did well learning how to test!
If you can hear the leak, you may be able to feel it with your hand -- just move your bare
hand along the hose.
Best of luck!