Most people think of Kayn as that terror that comes out of walls to kill them. To an extent, this build does just that. At least for the first 10-15 minutes. Constantly leave lane to roam mid or into the enemy's jungle and farm orbs off of them. If you can, try to target a ranged champion so that you can get blue form as soon as possible. You're basically trying to get your shadow form entirely for the benefits of an upgraded Shadow Step.
Once you have your blue form, stop paying attention to your team and start splitpushing. Now that you have an unslowable move that goes through walls and heals you on an 8 second cooldown, you can basically never get caught out and you can annoyingly go wherever you pretty much please. If you need to stall for your E, you can always R someone and wait it out for some time. Furthermore, you are not entirely helpless and you might even be able to duel other champions, who knows.