It just depends on the size and nature of the job. To keep it simple, here's a quick breakdown:
Touch Up Pen
The pen has a firm, chiseled nib applicator designed for small rock chips and scratches (think pencil eraser size or smaller). The correct application technique is dabbing small amounts of paint into the damaged area. Not for really long or deep gouges or scratches.
Touch Up Jar
The brush applicator is perfect for slightly larger damage (think thumbnail size or big scratches). The jar can also handle smaller stuff, so if you’re unsure about the pen, it's usually safe to go with the jar. Most people do, it’s our most popular product! You may want to consider purchasing a filler from our accessories page, too. Paint itself is not designed to fill.
Aerosol Spray Can
Aerosols are designed to re-spray an entire area (think hoods and bumpers). If you need to repair a damaged bumper or repaint your mirror cover this would do the job. Some of our customers will order enough to repaint the entire hood of their car (most auto hoods take about 4 cans). Remember: The key to a good spray job is preparation and patience!