Hi! I'm actually in the middle of doing my black ph2 sides, front and back.
It does take quite some work if you want it to look good but this is what you'll need.
Sandpaper, from
120, 240, 400, 800 to 1200 grit
Some grey
plastic primer
Paint, I'm using halfords colour match.
Clear lacquer.
And depending on how fussy you are on wanting a body shop finish and having a completely flat clearcote, you may want some
Cutting Paste.
Start off by using the 120 grit to strip off the texture of the bumpers, once you get to bare plastic go up to 240 grit and sand out the scratches, working up to 400 grit.
Wash the plastics with a decent detergent and make sure you rinse well and dry it off without leaving any lint on it.
give it a few coats of plastic primer (about three thin coats should do depending on how well you sanded it) leave about 15 mins between each coat then allow to dry over night.
sand it with some 1200 grit and wash it again to remove all of the dust.
Paint, again as with the primer work your way up through about 3 light coats, leave it over night and sand again with 1200 grit and wash.
lacquer should then be sprayed on in about 3 to 5 light coats to get a good finish. and after a week or two the lacquer should be hardened enough to flatten using rubbing compound.
Hope this helps, and sorry for such a lengthy post!
I'm off to finish mine!