I am still trying to wrap my head around storing barrels down. This subject is brought up on other sites and it always brings to me the same question, "just how much oil are you putting on." Two drops of oil or a light spray on a clean cloth is all that is needed to wipe down the metal parts after the gun is cleaned. If a side lock and you cleaned the inside with a Q tip and some Hoppes, a light coating on another Q tip is all you need.
I do wear gloves when cleaning my guns, but my fingerprints are non acidic and do not cause any rust spots.
The only time I store any guns barrel down is when I am running out of space and have to "double up."