My biggest concern would be the ability of a rattle can to hold up to UV.

I think if you polished it enough you could get it shiny...
but you had better not use the car outdoors or anywhere the sun could shine on it...

When I've painted things with Krylon (lawn furniture, bbques, non car stuff)...

they look great for a month or so.

If I was going to do the HUGE amount of Labour necessary (and I've painted, wet sanded, and polished my own cars before) I'd not want to invest 300hours labour for something that may or may not last 6 months...

I say go ahead and use the cheap spray gun and cheap compressor... go ahead and buy extra 2000grit paper to color sand out any perfections...

but buy a automotive type paint that is designed to handle the elements better... I'd much rather put an extra 150bucks into the supplies for the peace of mind on longevity.

Omni makes some pretty affordable paints.
and a buddy of mine used to buy close out auto paints, or mess up mixes... for CHEAP.

I think he would spend 25 bucks on paint, but he would paint the car with the color he could get instead having the full spectrum to choose from.

seems to me that my labour is worth more than $.25/hour
brant

p.s. I'm doing another auto paint job right now and believe me it is enough labour that you don't ever want to repeat it because you skimped on materials....