Rubbed the shell with sandpaper (not harsher than 180, i would recommend 240), then primed it.. Of course, i masked the key really well, as the little badge and the flash light hole.
I have to admit that masking the bagde and the light hole can be a real PITA...as can be the masking of the shell for the different colours..
But since you do the half one, you can use it as a guide for masking the other half.
May sound a bit !@#$ but definitely a diy job
Two coats of everything at least, including polishing