Paint on rear window chrome pieces, '65 Barracuda

DC 340, I've thought about dealing with the small fins as you mentioned. Brushing a sliver/chrome paint on the top then wiping off to reveal the chrome while leaving the paint in the crevasses. I may experiment on my spare set.
That's exactly what I did to my rocker moldings. They're also finned. Sprayed, then wiped the paint off the tops of the fins about halfway through the cure process.