Larcher,

In Africa, I have used a Birchwood Casey product called Sheath Rust Preventive. They come as a cloth in small packets, and when I have used them to wipe my rifle, it leaves a dry protective layer. Which keeps dust from sticking.

At home though, were it seems to always rain during hunting season, I have had best luck with Shooter's Choice Rust Prevent. It leaves a thicker layer which is more sticky than the Sheath cloth stuff, but since dust is not a problem when it's raining, it this doesn't matter IMO. It seems to protect against rust better than the many other products I've tried, and I'd probably choose this for a rainforest hunt.

Erik