I use the Hewes steel reels for 135 and 120 in steel tanks for black & white processing. I rinse the steel reels and let them air dry. I have never put steel reels in the microwave nor do I plan to ever.
The only plastic reels I use now are when I use the Jobo processor for color processing and occasionally for black & white processing. I rinse the plastic reels and let them air dry.