And with the can of refrigerant - there is a brass valve in this kit for that. Do I back the needle inside the valve away from the can and then attach it to the can (then turn the valve to puncture it), or do I leave the needle fully outward and screw it onto the can (allowing it to puncture the can as I attach it)? Seems to me it should be the former (so that there is no leakage as the valve is being attached to the can), but it seems to me I’ve read somewhere someone saying “now turn the valve to release the pin and allow the refrigerant to flow…” (meaning you puncture the can as you attach the valve).