How can I prevent this and get in front of it now? Clean it well with water. Polish the bore with Flitz, semichrome or JB. Then coat it well with a proper preservative grease.
Any water containing cleaning solution is fine. Windex is everywhere and works well. Take your pick. Any oil is fine for short term preserving.
Olive and other veg oils will polymerize, just like linseed oil, and make a gummy mess over time.
For long term storage I would never use anything but a petroleum based preservative. My guns are valuable and I will not sacrifice them to "historical correctness". The one exception is lanolin, aka fluid film. For long term storage LPS-3, RIG, and such are best. This idea that petroleum oils and greases are no good for preserving and lubricating BP guns is pure bunk.
Heavy petroleum grease is not a good shooting lube.
I believe the idea got started by people who observed that long ago petroleum was not available. However, that does not make the greasy part of dinner left overs desirable for gun maintenance. It is however better than the alternative at the time, spit. Keep in mind most old original barrels are rotted out from rust.
And now another oil thread will go on for 20 pages.