There's a lot of complicated ways of applying touchup paint (squeegee, syring, airbrush), but for simplicity, speed, and effectiveness, nothing compares to a fine-tipped artist brush:
Process:
1. Clean repair area with wax/grease remover.
2. Place 10 drops of touchup paint (purchased from auto parts store or dealership) in a paper cup.
3. Add 20% paint thinner. Stir.
4. Apply a minimal amount of paint to all chips/scratches with your artist brush.
5. Collect $25 - $40.
This will NEVER match the quality of repainting the entire panel or bumper. And the customer should not expect that quality for the $25 - $40 you charge them.
But, it will look better than the customer's attempt to touchup their scratches and chips with the Duplicolor or OEM nailpolish applicator.
Most detailers avoid touchup because they can't get it perfect. No touchup is perfect...it's always perceptible in close view. But with an approximate color match and a fine tipped brush, every chip or scratch can be improved for a price the customer is willing to pay.
