You probably know this, but “silicone rubber” is another term for RTV sealant. Widely available at auto parts stores and hardware stores. I like Permatex brand, but I don’t think it matters. Grease is an interesting idea, and might work fine.

Something I learned (luckily the easy way, research) is that there are two types of RTV/Silicone. You want the Neutral Cure variety, not the Acetoxy Cure. The Acetoxy variety releases acid as it cures (imperceptible amounts) that can cause corrosion. Neutral cures apparently release alcohol which is harmless to metals. The Acetoxy ones have a strong vinegar smell while neutral cures aren’t as strong.

Anything that says safe for metal should be neutral but you can read the labels to verify. Most hardware stores in the US carry GE “Advanced Silicone” in small tubes and dispenser tubes that is neutral cure.