On the plastic parts of the fender wells I used Krylon's (or maybe Duplicolor's) black spray paint specifically for plastic. It has held up for a couple years now without fading, peeling, cracking, bubbling, etc. It looks brand new still. All I did was was it really well and then mask off the area and spray two or three even coats.
For the rest of the fender wells and the exposed metal (frame, suspension, etc) I used black Rustoleum paint that was for propane/charcoal grills. I didn't do enough prep on getting the surface rust off, so it didn't last as long as a it should have. If I did prepare it properly I imagine it would still look great all these years later. But, some of the surface rust came back and other spots just started to turn grayish because I didn't start with a good surface and really just sprayed over stuff.
So what I'm saying is, the plastic parts are easy if you use the spray paint for plastic; and with the metal, good prep work is key for whatever you end up spraying-whether its paint, bedliner, or undercoating.
