Another question about filling with a tank...

Is there any special trick to it? On my tank it has an arrow pointing up that says "gas" and another pointing down that says "liquid" in terms of how you want the stuff to go in to the system. I know that with cans you are supposed to rock the can side to side to get it all in, but from what I've said not with a tank.

I'm assuming that I just let the tank sit on it's own and not touch it, the liquid will turn to gas anyway, but I wanted to double check before I accidentally waste some precious R12.