I have a 99 catera and I'm going to recharge the A/C again just checked the system and it's O.K. My question is what is the besat way to hold and shake the can while filling. I read directions but the way they are saying to do it wich is hold can upright and shake from 12 to 3 but that doesn't seem to work to well. Can someone please tell me the best way, it seems when i hold and shake any way it works o.k but i dont want to shake too much. If anyone knows the best way please reply or if you have any other feedback would be greatly appreciated....