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GitHub User: jbarket
I ended up creating a library to expedite the creation of various fields using Ransack that I obviously think is worth checking out: https://github.com/jbarket/facet_for
Basically, you call f.facet_for :field_name in your search form, and it takes a smart guess, which you can then supplement. It was really created for a large project at work, so the documentation may not be what you'd call extensive... but neither is the documentation for ransack.