You can oil them for protection against rust. However, contact your manufacturer beforehand as some handpans don’t work well when oiled.
Use a clean cloth to remove any dust, stain, or moisture. Using a microfiber cloth would be the best option.
You can also use rubbing alcohol for cleaning stubborn stains, grease, or any spill.
Remember to also clean the insides with a cloth or isopropyl. You can use a blower to dry the inside to limit the chances of rust.