It is easy enough with the right tools, some people suffer from the paint flaking and fading, Seen a bad example of a colour coded clio today, wish I took a pic. The paint looked extremely tacky lookin.
It normally involves sanding the plastic down till its smooth, then making sure its clean prime it, put a few layers of spray paint on and then laquer. Thats what Ive been told anyway, have been thinkin of doin it myself but dont want to risk the thing going pear shaped.