For a few years, I travelled on steel boats on oceans. Rust was an unforgiving enemy. I never found one product that would keep rust off, forever.
Heavy grease will abate the weather for a long time but will pick up dust and dirt on the road. Oils will penetrate steel and offer some protection. I haven't had good luck with dry lubricants.
For moving parts on trailers like stabilizers, I use chain lubricant in a spray can. It is easy to apply and seems to work good keeping the parts operating. The chain lube is sticky and will hold some dirt or dust but not enough to interfere with operation.