I have found that the following works for me and it also provides a good
reason to get the wife a good microwave oven. Place the shell (except
Cypraea) in a paper bag. First pour a little water into the aperture and
place in the microwave. Turn on high until you hear a "POP" sound. Remove
shell. The remains will be plastered to the inside of the bag. If there is
still some left in the shell, it is now cooked and I have found that when
cooked there is little or no odor. Works for me, but for some reason my wife
won't believe that I bought the microwave for her and just thought of the
shell use afterwards.

Frank (Still cautious in Massachusetts)
Gems From The Sea
www.shellgems.com