Well with the military aircraft I work on it seems that in some instances the panel lines are very visible especially ones that are removed quite often. And very few panels require sealant on them, only in high stress areas.
Rivet lines are still visible as they have a tendency to accumalate oils and dirt over periods of time. Thus making them quite visible to the human eye even at a fairly moderate distance. Doing a recessed look to these rivets in the paint itself would look realistic. Rivet lines on bare metal surfaces are ofcourse very visible.
To get away with making these panel lines very visible they'd have to be high use panels. Use some variance in which ones are more visible than others. Nicks and scratchs around these panels would be something that you could use too. I highly doubt they were very stringent on paint jobs during WWII especially at forward deployed locations. And I also doubt they were doing constant washes on them either. Even in todays birds they don't get washed constantly. Hence why you see alot of oil/hydraulic streaks on the under body and wet streaks where fuel cells are located.
I think weathering a paint job is a good thing as these are fighters not public transport aircraft. These weren't made to look pretty and dull spots in areas to indicate some kind of touch up over time and patches would be something to think about. The problem is how far to go when weathering. Too much makes it look fake and too little just doesn't look right either.
