Re: spray can paint job.
Always wipe the area to be painted with Prepsol/prepsolv, or at the very least denatured alcohol.
Follow that with a tack cloth.
Spray a fairly light coat, then wait 15 or so minutes before continuing (read the can for the best time)
Spray as wet as possible without getting runs or sags. (that takes practice)
Spray with the can perpendicular to the surface...not in an arcing movement.
If you do get a run, you can either wipe it ONCE then respray, use a heat lamp to flatten it (takes practice) or wet sand afterwards and respray the area.
For a really nice job, even if you use enamle, wet sand (AFTER IT'S THOROUGHLY DRY) with 400-600 grit and spray a final coat.
Next lesson, you can get a very close to spray job with a brush if done right.