This is a setting spray designed to be used on damp, naturally curly hair. You might not get the results you're looking for if you use it on dry hair. Many people with straight hair tend to have heat-styled curls fall if their hair becomes wet. My suggestion is that you might want to look for an aerosol finishing hair spray that is designed to go on dry hair.
I have naturally curly hair. I use this setting spray when my hair is damp to hold my curls in place while I am drying them with a diffuser, and it does a great job. I was not getting good results when I used it on dry hair. My stylist explained that setting spray is used on damp, naturally curly hair before it is blow-dried. She recommended a Moroccanoil finishing hair spray in an aerosol as a finishing spray for dry hair. Maybe you could check with your stylist and see what they recommend. Good luck and I hope your prom is fun!
Because you are going to have your hair curled while it is dry with a styling iron, I would instead ask your stylist for recommendations for a strong hold finishing spray designed for use on dry hair. Setting sprays like this one tend to be pretty wet, and it might not be a good choice to use on dry hair.
While this product works great for naturally curly hair, I really do NOT see it holding in a style set at the hairdresser for hours on end. It just isn't that strong of a hold. Good luck!