I've read a lot of different accounts of how they contended with corrosive ammo, but nothing consistent on the process they actually used in the field. Also, how often were they expected, or were able to clean them in a combat zone?
You might be best served by posting this in r/guns.
As with today, the field manuals outline the expected care for issued rifles and equipment.
As an example:
FM 23-6 covers the M1917 .30 Enfield
FM 23-7 covers the M1
FM 23-35 covers pistols
FM 23-15 the BAR
The technical manuals covered what what ordnance teams would look at to service guns that needed maintenance.
TM 9-1270 covers rifles
TM 9-1295 covers pistols