Someone talk me through getting rust off cast iron?

steel wool or a stiff brush with a bit of water, scrub until you're back to bare grey metal. for really bad rust you can soak it in half white vinegar half water, but check it every half hour and don't leave it more than an hour or so, the vinegar starts eating the iron itself once the rust is gone. then rinse, dry it straight away on the hob over heat, wipe on a very thin coat of oil and bake it upside down in a hot oven for an hour. do two or three coats. the classic mistake is too much oil, it goes sticky instead of hard. wipe it on and then wipe almost all of it back off.