Hmmm,
To me the cowling and the lower rear trim would be 2 different issues (based on the two pics):
The rear trim's easy. APC with toothbrush or the like, wipe dry with terry. Let dry. Apply water-based dressing, haze, buff, etc. If that doesn't meet spec, move to trim dye like Black Again or B2B, whatever you use. If that doesn't work, include that piece of trim in the cowling job.
Cowling: Pic is kinda iffy but looks like fading, maybe tiger-striping. Either way, try above on small area. The little fins will be tough to get at; for even coverage you can use those little foam wedge brushes like the art supply store or Edge's foam brushes. If that don't work.........
I find myself painting cowlings more and more now. When they're toast, yeah, dressings and dyes look good when the cust pays, (and to some, that's all that matters), but for just about the same amount of cost and a bit more labor, it's an easy upsell. Cust should understand that this will keep looking good for years. They will go for it 9 times out of 10.
I like SEM paints and dyes. On plastic there's no need for self-etching primer, just go with satin black (or gloss, based on vehicle) One can will do the cowling, and then some.
Pop the wiper arms off (and paint them too, if neccessary). Usually a little plastic cover above the bolt. HINT: Open the hood to ensure you get the whole piece all the way down to the top of the firewall. Mask with quick release 3M tape, newspaper.
If there's a body shop supply near you, you can pick up: tape, masking paper, plastic car covers (for easy overspray prevention) SEM paint, sandpaper all in one stop.
PREP the cowling with Plastic Prep, let dry, scuff if needed with ScotchBrite and/or sandpaper, Plastic Prep again, dry. Grab a cold beverage and the can of Trim paint. Shake VERY WELL (the paint), apply several LIGHT coats , better than 1 or 2 heavy coats. DON"T Rush, FOLLOW THE DIRECTIONS regarding flash time between coats. Done!
Sometimes, a light coat of SEM Clear can be used.
Whew!
Good luck, zesty!
