I use an opened wire coat hanger and LARGE plastic fish bag as the net. I place several clothes pegs on the coat hanger to hold the bag open and gently coax the fish into the bag. - Easy since its clear. Once it is in the bag I deftly close up the bag top with my habds, unpeg the clothes pegs and then use a BIG fish landing net to scoop up the plastic bag with fish inside and into the new tank or esky or fish transport container. You can expell quite a lot of the water from the plastic bag before lifting. The plastic bag is simply to protect his slime coat, not to contain water.
If the fish is 20 inches long, use a plastic bag about 20 inches wide. Try some barrel companies as they sell 200 micron plasatic barrel liners very cheaply. You could also use a pillow case but I find cotton rougher than plastic.
If you get really stuck you can also use clove oil as anaesthetic. It will knock out all the fish of course and drain most of water from your tank to save oil. PM me if you need more accurate instructions with clove oil.