It is easy. I use the crochet hook method, too. You use a different color just so it's easier to see to pull out and put the needles back on the stitches.
There are many reasons to use it. For instance if you're making a sweater from the bottom up you can go back and add length or a design. It also works on sleeves and necks.
You can use it on a shawl or scarf that has a one way design. You'd start in the middle with a provisional cast on and work the one side, then pick up the stitches and work out the other way.