this is how i did mine....
first off remove the 2 10mm bolts
then remove all seals etc
flat or scotch the roker cover useing 800grit went n dry) (or red scotch)
apply a few coats of primer (heat proff) not sure if you can get it anywhere or weather its just we get it becase we area bodyshop

then guide coat the primer (get a diff colour aerosol and just lights spay over the cover so it looks like overspray) then flat it again useing some wet n dry (800's) untill all the guide coat has gone and it looks like it did before you put it on

clean off useing some panel wipe (white spirit will do the same thing)
then your ready for paint!
then re fit (mayaswell buy a new seal aswell while your at it only cheap and you hvae a guarantee its completly dirt,dust etc proff so wont do your engine anyharm