Basicly, if you can remove the lenses, aperture and everything that could be damaged by either solvents or heat that should be a start.

Next I would put the part with the flange in boiling water and see what happens.
You will need 2 oven-mittens to protect jour hands.

I would not put a burner to it or put it on an electric heater element.

Expect discoloring of the brass and I realy think this is a complete restauration project to start out with.
You might have a look at the Large Format Forum, there are a couple of threads about it.

Good luck and be carefull,