You're basically giving it a steam bath. "I've found the easiest way to ... "Afterward, wipe it off with a warm, damp cloth," which should leave your microwave clean and subtly scented.

The resulting steam was channeled through special chambers ... The final room was the Caldarium, a steamy hot room which might also have a hot plunge bath, or labrum. After all this, the oil ...

You're basically giving it a steam bath. "I've found the easiest way to ... "Afterward, wipe it off with a warm, damp cloth," which should leave your microwave clean and subtly scented.