They are left-hand as well.
The left hand thread is less likely to become unwound during revolutions of the cylinder and jam the ejector rod. Thus S&W figured out the left hand thread.
I remove the cylinder and clean the barrel, frame, crane and cylinder. They I lubricate (everything for a blued gun, just friction points for a stainless) and reassemble. I give blued or plated guns an exterior coat of oil, it might be a while before they get another one.