When you light olive oil in a metal menora, some of the oil invariably finds its way into the cracks between parts of the menora. How do you remove this residue?
Put water and dishwashing detergent in a basin; let the entire menora soak in it.
People have told me soaking it in ammonia also works. I soaked my oil glasses in ammonia for a couple of days and it worked pretty well. I did keep it outside while I was soaking it because of the smell and because I have little kids around.