Yes, you can take an empty oil can on an airplane. The oil can must be cleaned and can not have any residue in the can. The residue can be cleaned by using hot soapy water.

You can use a little bit of Clorox and some mr. Bounty liquid that will do the job

I just keep washing it off with a clean dishcloth and water. It is mostly just soapy residue, so rinsing it off with water should do the trick.

Spray WD40 on to it and then rub with a cloth.

Or soak it in hot soapy water for 30 minutes or so and wash as usual.

The zester should be soaked in soapy water to soften the food residue, then cleaned with a stiff brush, such as a tooth brush.

Either with a high pressure hose and some soapy water or just use a normal hose with some soapy water. Dont worry about drying, on your first drive after the wash the wind will take off all the residue