i used flat black krylon fusion for plastic, i did no prep b/c that's what it recommended - i just scrubbed them with soap and water
i've been pretty happy with mine - i got a couple chips on the front one - but to be honest i don't think there's any paint that will not chip from a rock or something
the front one is cake to take off - there are 6 little tabs you just have to push in from the outsides toward the center of the it - you can kind of do them one at at a time and pull a little on the front at the same time - be careful not to push too hard they are thin plastic and will break - there's no need to take off the grill there's a nice big hole you can reach into right in front of the hood latch
for the back one you will need either some fishing line, a credit card or i like to use a bondo scraper (carefully) and some goo gone - it's held on by adhesive tape around the edges and in the center there are 2 little holes it just sits in -
so you just have to carefully go around the edges and it will come off
to put it back on use 3m adhesive tape - i used a roll i had and cut it into little pieces to go around the whole thing