i have heard from various sources that stripping all of the paint is sometimes a bad idea. mainly bc of imperfections in the metal. i guess those coats of primer help straighten things out.
How very true, Yat Ming is like the surface of the moon when stripped. What I do in those cases is polish the surface till it's nice and smooth and then start painting.
What some people do too is if the chosen color is close or darker than the original one, they just lightly sand the surface with fine steel wool or one of them 3M pads and paint over that. Only thing is, you might end up with a thick paint finish hiding some detail. A coat of primer is also recommended but that will only compound the problem.