When you're painting a panel, door or whole car, you often find yourself seeing flaws in the surface. While those flaws are on your mind as you find them, they are easy to lose sight of later. Eventually you forget where some of them are and only see them after spraying your finish.
We find that there is one sure way to "remember" those flaws. We've used it for many years, and it's never failed to help us take care of defects without losing them. It's also about as cheap a solution as can be: chalk. That's right; just keep a stick of chalk (any color) in your hand as you inspect the body of a car or just a single panel. When you find a flaw simply circle it with chalk.
When you come back later to fix all the defects, you can wipe the chalk away as you go, or wait until you wet-sand the surface. Chalk doesn't mar any finish and doesn't chemically react with undercoats or top finishes. Unlike other methods (bits of masking tape, dabs of white-out, Post-its) that might leave a blush in the paint, chalk just goes away during surface preparation.
– Second Chance Garage