Removing sand from tiny wentletraps

[sdsheller]

I live in San Diego County, California, and found some empty but perfect Epitonium tinctum specimens. They are semi-transparent, and have dark sand trapped far up in the whorls. What is the best technique for removing this sand? Attempting to fill with water and shaking isn't enough. I have thought of a water pic, but don't own one at the moment. Any tips would be much appreciated.