Advice please on shooting in extreme cold

I have a week in Iceland next month and expecting average temperatures about -10 degrees C.

Coldest I experienced recently was in far north Norway in April and I had a few problems with the batteries on the M9 (as expected). I guess I just want to ask if anyone has tried to shoot in the cold in Iceland or equivalent and what their experience and advice would be to maximise my enjoyment.

I am guessing a DSLR may be a more appropriate tool for some of the long exposure plus ND filter shooting I plan on doing. I would especially welcome advice from anyone who has shot with a rangefinder under similar conditions.

Many thanks.

David
Australia