True, then once the compressor starts after about 45 sec, turn the can
upright to charge gas. Charging straight liquid can lock up the converter if
it's not really low. I always do a little of both when charging from the
small cans, and you can lay the can on something warm, but not too hot, to
slightly raise the pressure in the can and help force it into the lines.

Also, you can unplug the low pressure switch, and jumper it with a paper
clip. It'll be in the suction line somewhere or on the receiver (low
pressure hose which is the larger of the two hoses) When the can top gets
cold you can tell the refrigerant is moving through it, then plug the low
pressure switch back in.

Those are just backyard suggestions, the proper way is with gauges and a
reclaim system.

Spdloader