Rustoleum is noted for its coverage. There are some similarities with spraying in that the basecoat colour (ie whats already there) dictates how many coats it'll take (going over red with white can be hard going for instance) but usually three coats will obliterate any colour beneath. Its also very tolerant of other paint types although there can be exceptions and seam sealer can sometimes be an issue if you haven't let it cure fully.
I'm actually far less concerned with getting a perfect finish and I'm sure others will have already surpassed me on this. For me its about obliterating the shabbiness and fully identifying where I really
DO have corrosion issues rather than where I
think they might be. So on that basis I'm not in the least bothered if a year later, rust bubbles up somewhere - it just enables me to concentrate on those areas and decide if a new panel is the answer or more intensive grinding. Either way, it only takes a few goes with the roller to bring the suspect area in line with the rest following any remedial work.
For me, thats the biggest plus of this method.
What I hadn't anticipated was just how big or how far-reaching this thread would become, or indeed how many smiling faces it would create.