heat gun regulating

Cheap 2 setting heatgun (too hot amd way too hot) i want to throttle down the heater and maybe even the fan for a hot air reflow project, i need it to be 250C/485F max with little airflow. Looks like the temp range now is like 750/1100F.. could i put in some sort of rheostat or huge resistor to cut power to the heating element or is it going to be a duty cycle thing, maybe controlled by a relay and a high speed 555 ic timer?