We haven't had any feedback from anyone using Soto's Appliance + Porcelain Touch Up for the interior of a car, so we are not sure how it will work. It may depend on the surface (we know the paints work well on metals and many other surfaces; they haven't been tested on plastics), and because of the variety of surfaces in a car, you will just need to test it and see.
All of our products are exceptionally durable once fully cured (they will be dry to the touch in about 30-60 minutes, depending on environmental factors, and will fully cure within 1-2 weeks or less, again depending on environmental factors). The paint is designed to cover scratches and make them less visible, but deep scratches may need to be filled first or perhaps they can be filled by using multiple coats of the paint. The Appliance + Porcelain Touch Up is a high-gloss paint which will match shiny surfaces, and the Multi-Surface Paint Touch Up is a low-sheen paint which will match matte surfaces.
