You can make the transfer just fine as you've described.

Just be sure you pull a good vacuum before you start and purge the lines of air. Really a good way of recovering most of the R-12.

Another way to recover most of your R-12 is to get a cylinder (like a 20lb BBQ tank) and install the proper fittings so that your guages will hook up to the tank. Then put the tank in your freezer overnight and it will pull all of the liquid out and most of the vapor too. Just make sure you don't have any air in the tank or lines. You will need a vacuum pump to get a good vacuum on the tank before using it.

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JD