There are commercial adapters available, that essentially are tank
fittings on both ends.
Try Cabella’s or other sporting good stores.
The instructions tell you to put the empty tank in the freezer which
will let you get more propane in it, but if you have a vacuum pump
you can make better system with a “T” and valves.
This takes some common sense and care but, works quite well.
An even better system can be built if you have access to a liquid
propane tank (one which take it’s output from the bottom of the
tank), but that can over fill tanks!