boiling water could also be causing flash rust. my traditions kentucky always rusted with HOT water. I use warm water now.

Also, rem oil will attract rust by doing what you did. Get a good layer of it on a patch, push the patch down using both sides of the patch. Give it a few minutes to dry and then use one dry patch to mop up the excess oil. Before oiling, i always use some windex patches and run a few down the bore and dry it.