Been re-trimming out a few old windows on my house with AZEK (PVC trim).
I screwed it to the house and touched with heads with some caulk, but it looked like total
(because you can’t sand caulk).
Don’t know why it took me so long to learn about it, but a contractor friend told me about a product called “Bond & Fill.” It’s a structural adhesive made for PVC trim, but it also works great for filling nail and screw holes because it cures in 5 minutes and you can sand it flat and paint it the same day.
Sorry if this sounds like a commercial, but this seems like pretty great stuff. I’d thought of using Bondo, but Bondo always ends up popping out of the holes due to movement of the wood/PVC.