Hi Charlie, The general method of refilling a small liquid gas tank is to connect from the bottom of the supply container to the top of the tank, if the supply is a disposable gas cartridge, then hold it upside down.
ALL equipment should be in good condition. The reason to fill in this manner, is to ensure liquid (not gas) is transferred, and as the liquid 'sprays' into the tank it chills the tank, allowing a better fill.
Where I worked we had large liquid gas storage, These had inlet 'valved' to both top and bottom, When the supply tanker was filling, if he filled from the bottom only the quantity was curtailed because the pressure built up too quickly, if he filled to the top only he could reduce the internal tank pressure get a good fill, but stop the production line through loss of gas pressure. Slightly easier for a small tank that is 'off line'
Hope this helps
Tom