For a serious answer:
My experience is only on captive NG cars, ie. not interchange. Step one, blue flag protections if required. Step 2 disassemble brake cylinder and inspect for pitting and worn brake cylinder piston cup. Step 3 clean cylinder and piston assy. with solvent. 4. grease cylinder with brake grease and replace piston cup if damaged or badly worn. 5. remove and exchange triple valve with rebuilt one or disassemble removed triple valve, clean and lubricate per procedure in effect. 6. reinstall rebuilt or cleaned and lubricated triple valve. 7. Test car with single car test device or test serviced cars as a group using a locomotive. 8. adjust brake linkage travel if necessary and 9. inspect and or replace brake shoes as required. 8&9 aren't necessarily part of the COTS, but probably would be done coincident. 10. paint out previous stencil and stencil new date which is the date the cars have passed test and are ready for service. 11. remove your blue flag before you go home!