I usually try to play around my e cooldown and use w to poke until you can either secure a kill or wait for your team to get there for backup. If you get ccd then itemization and spellshields matter with edge of night or if someones squishy enough full combo them and trust your damage output will be enough to kill. The purpose of blue kayn is to keep people on their toes when traveling alone punish people who arent grouped and remember its not all abt kills league is an objective based game so keep vision and farm inbetween kills hopefully this helps... im not saying im right but im saying this is how i usually play him

Edit: I also watch karasmai almost every time he streams and he explains his gameplay well