Give it to your squire.

I usually attack it with a terrycloth and some Flitz. A little will go a surprisingly long way.

There are various methods of oiling, waxing, or otherwise preserving it afterwards. I prefer boiled linseed oil for that, personally.

In Ye Modern Times, you could also just make your mail out of something that doesn't rust. I didn't, though.

Angle grinder and a buffing pad with a heavy dose of Sex Wax

Toothbrush and time

Clothes dryer and a bucket of sand would probably work.
Plus you can sell the self-dismantled dryer for parts after.