Regardless of what fluid you use, when it is very cold out, if you just shift much faster, especially from 1 to 2, it will help it to shift smoother.
The fluid slows down the gears FAST as soon as you put the clutch in..
In -20 type weather, I found that until it warmed up a little, I would go from first to neutral, let the clutch out and spin up the trans, then put it back in and shift to second.. double clutching on the upshift....
Saves wear on the synchronizers.....
Jeff