[Coley]

I think the rattle can thing works....but it is a last choice within reasonable choices for that particular task.

Rattle cans are great for smaller areas, detailing etc....but when you start to have to cover the square footage of an 18ft truck the scale of advantage vs. effort and results disappears in a hurry I think.
I think once you start buying a box of 16, 20, 25 cans of rattle paint.....it starts to become clear that you aren't on the best road for a paint project, lol.
Let alone the putz around time shaking cans, grabbing the next one, paint-appearance continuity, etc, etc.

At that point, a compressor (even renting one), a spray gun and some basic paint will go faster, farther....for not too much more money I think...and this was well mentioned by Problems and others.

My two bits.

Coley