You can use the single-pronged transfer tool to cast off in two ways: in front of or behind the sinker posts (gate pegs). The first is quick and easy, the second gives a better finish.
You can cast off your knitting using a darning or tapestry needle. Method 1 uses a quick running stitch which is good for swatches although a the edge is a little uneven. Method 2 uses a back stitch which is slower but gives a neater finish.