No matter what kind of paint you use (powder coat, automotive, rattle can) you're always going to get scratchs and dings. Rattle can paint is GREAT for bikes, can always do touch up work with a little paint brush (spray a little paint in the paint can cap to dip your brush in) or mask and spray.
If you have a really deep scratch or chip you can spray or brush on some primer (usually has more paint solids to it and drys fast), sand with a scrubby pad or 320 grit paper then spray on your color. Probably take a couple coats of your color to completely cover the primer.
To minimize the "orange peel" effect with rattle can paint, run the can under hot water for a little while before spraying.
If you want that really BRIGHT shine, after the paint drys, rub it out with some rubbing compound.
Only draw back is the rattle can paint doesn't hold up to gasoline. I always put a rag around my gas tank spout when putting gas in yet there's still always a drop that splashes somewhere. A little rubbing compound will put the shine right back.