Dont forget that the wings on P-51s were lacquered, not bare metal.
Most of the the Warbirds are as well... "Gunfighter" and "Red Nose" get polished, but yep, the're laquered and Bondo-filled as well.. Here's a Warbird wing..
Shiny, but not NMF.. And no panel line, 'cept the gun-bays..
Since we're talking about it, it's right in the P-51 Maintenence Manual about applying silver laquer to all surfaces of the aircraft anywhere it's un-camouflaged.. This includes many interior surfaces as well, BTW... I need to dig that thing again and post it, because it answers a number of "What colors are the P-51's Interior surfaces?" posts... (There are NO unpainted areas in it, BTW..)
I remember taliking with Dad about polishing up his fighter to get extra speed (we were wathcing an episode of "Baa Baa Blacksheep" where one of the pilots was doing so to his Corsiar and he said it was a lotta bull... Pilots had many ground duties to perform, but none of them were to go out to the line and polish their airplanes...
The Crew-chief did the cleaning, if any was needed, but only on what they had to handle to keep it flying.. The airplane often flew more hours than the assigned pilot did.. Putting it politely, If a Line-chief saw a crew-chief out hand-polishing his aircaft, that meant he didn't have anything better to do, so that meant that the Line-chief would grab him and put him to work somewhere else where his time would be "better used", lol..
Anyway, I'm a firm believer in Krylon's Silver Foil Metalic for NMFs ever since I found the stuff at Hobby Lobby.. You can make all kinds of different-shade panels with that stuff and judicious undercoats and masking, along with judicious masking for clears.. And it dries hard, with no metallic getting on your fingers after it cures..