korstmos

Depends, how much do you care, and how good does your car still look?
If you drive a pristine car that you plan on selling eventually: get it done at a bodyshop.
If you drive an older car or plan to keep it until it dies, and dont care about the looks too much: chrisfix has some good videos on working with a paint pen

If you drive a 20 year old car in the rust belt: lol

To use variable pricing to get you to pay the most amount possible, or to convince customers that are on the fence with a clever salestalk or small bonuses