Like MTNJeep said, that will work for plastics. I have seen people heat up metal with a heat gun and us compressed air in the can up-side-down to rapidly cool the dent and have it pop out. You might try that.
This Rugged Ridge Cowl Armor is the other option for "fixing" the dents. Some people like them, some people hate them, but they work! Let me know if you'd like a quote or have any questions.