Since the Sharpie ink soaks into the surface of the ball and the weight is negligible, I expect no change in ball performance from a blank ball. Adding something that creates a change in the surface like a paint/nail polish on top of the surface could create turbulence that would affect the flight in some unknown way.

Besides, my wife already wonders about the amount of time I spend adding a mark and extending the line for easier visualization for putting. Having a tray to hold balls in position while the polish/paint dries would be over the top. ;-)

I think Testors or nail polish will affect ball flight if the coat is too heavy. The sharpie marking isn't raised enough to affect aerodynamics. Give it a shot, video some results! :D

Go to a craft store and get any outdoor acrylic. Coolest though is glass paint...its iridescent!

Here's what I use. Titleist's customized ball and "Golfdotz" to mark them more. Got another back this morning that someone found on the edge of a hazard. Excuse me.......penalty area.

Sorry forgot the photo

Used to use nail polish but that had 2 problems - it took a long time (comparatively speaking) to dry and it tended not to last long. Sharpie is way better.