It turns out you can fix a lot of dents by just using your phone. Many insurance policies will cover certain types of dents – such as those you get from weather like hail. Dents from an accident may also be covered – by your insurance or someone else's. This varies by state, by insurance company, and by plan.
Using a plunger to fix a dent is the oldest and most popular method. As many people find out, it's not always perfect. A wide, shallow dent might be fixed by a plunger or other method of suction...or it might be made worse.
Too often, the result is the opposite of what you intended. You need to push the plunger pretty hard for it to get the right seal where it will pull a dent out. This can result in making the dent worse by pushing a section of it in. You risk making the dent deeper and broader this way.
It also involves flexing the metal, and this can crack your paint. Many people end up making a shallow dent that's easy to overlook appear far worse because now they've damaged the paint job and called attention to the area.
If you do try it, use a plunger for a sink. These are more regularly shaped and shallower, requiring less force to create suction. Plungers used in toilets require a lot more force, increasing the chance of causing more damage.
A Hair Dryer...
This method is just a waste of time if used on its own. It can also risk damaging the paint and finish. To get metal hot enough to push the dent out easily, a hair dryer just doesn't do the job.
...or a Heat Gun?
Nope. Just avoid this. There's much more risk that you'll damage the car in a way that's far more expensive to fix than a simple dent is. You're almost guaranteed to ruin the paint and finish in an area.
Simply put, anything that gets the metal hot enough to push out the dent will have already ruined the paint, finish, and created a more expensive problem to fix.
Dry ice is 109 degrees below zero. If it comes into contact with your skin even for a fraction of a second, it can cause immediate frostbite. People have caused themselves permanent damage when working with dry ice without training.
That said, this would have been a decent answer for cars made in the 50s and 60s. As dents rapidly cooled, they might pop back into shape. Yet by the 1980s, bodies were made of thinner metals that do not respond the same way as early body materials did.
Above all, though, don’t risk your safety!
Dent Repair Kits
There are a number of products that are described for dent repair. Some might work and some won't. The best thing you can do with these is to read the customer reviews that are available.
Other customers might reveal details that help you make a decision about one product over another. If a drawback is repeated in multiple reviews, be realistic that it might happen to you.
Don't treat these reviews as gospel. Every dent is a little bit different, so you could also find a good product that just doesn't work well on the kind of dent you have.
The most thorough dent repair isn't DIY. It's professional dent repair done by experts with access to tools of their trade. It also comes guaranteed, which is really the only kind of 100% surefire way to know that your dent will be fixed properly.
DIY methods can work. Just do your research and be realistic about what they can do for you...and what they risk in further damage. The deeper or narrower a dent, and the more likely you'll need professional repair to fix it.