Which film MF system has the best weather resistance? I work a lot in nasty weather, and as I shoot more and more film I'd like to be able to use film on those days and places too. Thanks.
Not really weather "resistant" as such, but water won't hurt it noticeably, and when it does die, it's only $40 for a new one. If you need a "system" camera, the Diana F+ is built much like a Holga but has interchangeable lenses.
I use a rain cape on my Kowa SL66 or Yashica D, additional rubber bands, does a fairly decent job in a drizzle or light rain, not so good in a steady hard rain. Other than a underwater housing for a Rolleiflex ro Hassy not sure if any MF is really weather sealed.
Might give you idea on making your own? Seal around the lens filter and underside openings for hands. Ofcourse any water on the lens filter will create an issue.