Mage only Zulrah with twin flames staff

Hi all. Learning Zulrah atm (10kc). I’m using twin flame staff and tome of fire. Just wondering if I should be casting fire surge, or should I be using fire wave to get the second hit effect from the twin flame staff?

Sorry if this is a dumb question. I’m only just delving into bossing and I haven’t played osrs in like 5+ years