Choosing your product really depends on what you are looking to achieve and what your damage looks like. 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 (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 the smaller stuff, so if unsure about the pen, it's usually safe to go with the jar. You may wan't to consider purchasing a filler from our accessories page! Paint itself is not designed to fill.
Aerosol Spray Can - Aerosols are designed to re-spray an entire area. 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 for good coverage). The key to a good spray job is preparation and patience!