Shiranui was helping Zoro practice his illusions.  Thanks to some help from some of his other teammates in the form of providing visual aids, the Zoroark was able to pull off convincing illusions of moves he couldn't naturally use, one of which was a convincing Fire Blast illusion thanks to Higitsune's help.  Shiranui knew the illusory moves were mostly for the contests, but he did have a few thoughts of using the odd illusory move to keep his opponents on their toes.