cast iron rust inhibitor / paint prep for cold temps?

Hi,

I'm slowly working on my Van Norman 22LU, and currently it lives in an unheated garage
in an NJ winter. I had finished needle scaling off all the paint, but didn't get
it primed before temperatures dropped. Now it is pretty consistently too cold to
paint (I was going to use S&W kembond, which wants 50degreesF for 5 days). Heating
the garage for long enough to paint the machine isn't really practical.

Unfortunately the machine is slowly accumulating surface rust on the exposed cast
iron. I'd prefer not to use any of the normal metal preservatives (e.g. boeshield) or oil,
as that would just need to be removed prior to painting in warmer weather.

Anyone have suggestions on a rust dissolver / neutralizer / paint prep which could be painted over with minimal additional treatment?

Thanks!
-Phil