Hard.
A proper paint job invoves taping over all the windows, trim, badge removal & what nots.
Then you need a clean, wind free room. You need to know how to mix the paint, apply it properly, allow for dry times etc...
Then, most paints need a buff when they're done & completely dry to fully shine & remove any "orange peel" or thicker layers of paint.
It can be done if you've got the time, the space, the $$ and another car to drive while you're doing it.
Hell if you do good you can open your own paint shop!!