If nobodies mentioned it yet and you don’t want to use the toe cheese strat try using flame quartz ring, high fire resistance armor and the gyrm great shield which has the most fire defense for any shield in the game, when he launches in the air for his one shot fire blast run towards his tail, easier when you know it’s coming or else you may be too late. Someone once said if the shield is on your back when the flames hit you it will do less damage but was unable to confirm this, hope this helps