The problem: Painting stuff without removing it from the car. You know, that linkage on the carburetor needs some color but you have to do it without painting the carb itself, the intake manifold or valve covers. Or, maybe the panel holding the radiator could use a coat of paint but it's too much trouble to remove the radiator, hoses, brackets, etc. Maybe you're dyeing the door panel and need to mask the handles, or touching up a small area of the dash. Using newspaper and masking tape is difficult, time-consuming and frequently lets overspray through.
This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2006/07/06/masking-made-easy