Wet sanding won't do anything but knock down a rough finish if the grit is lower than ~1600-1800. The dark metallic blue 10 year old Maaco/Earl Sheibe paint on my '68 was oxidized so badly it was easier to wet sand it out. I only had grits up to 1200, but that was fine enough to allow polishing compound to shine it up afterward. A finer grit paper would have needed less elbow grease with the polishing compound. Now the paint looks pretty good from 10-20ft away, but the body itself needs some attention.
Long story short, wet sanding with some really fine paper and polishing afterward will definitely improve the finish even on rattle-can paint. Throw some good thick wax on top and it will look good.
Long story short, wet sanding with some really fine paper and polishing afterward will definitely improve the finish even on rattle-can paint. Throw some good thick wax on top and it will look good.