P-38s were flush riveted. A coat of paint would often hide the rivets to the extent that they could not be seen from just a few yards away. I have photos of the various aircraft I crewed in the Navy. You cannot see the outline of the rivets in the photos, and some were taken just a few feet away.
I think that too much emphasis may be placed upon details that simply will not be seen. Panel lines show up, especially removable panels such as cowling and accessory panels.
Here's a photo I took of a P-40M. Notice you only see hardware removed on a regular basis, access panels. Rivet lines are undefined due to being painted.
My regards,
Widewing