[Ruy Dias de Bivar]

**The typical answer has been to liberally coat the firearm in some sort of viscous grease (last generally sold in the Korean War era)***

Vaseline Petroleum Jelly, or equivalent will work just fine.

[Blueflag]

True - now, get it all off, including your optics/sights.

Vaseline is horrible about ‘attracting’ and holding dust and grit.

Just sayin’

[Hardastarboard]

Common axle grease sold at the local auto parts store will work. It is intended to be durable under pressure, heat, friction, water and salt exposure.

Having said that, Vaseline is a byproduct of extracting oil from the ground, and is essentially just grease with no additives.