another panel line quest.

I am building a Gundam perfect grade model, and I really want a realistic look to the weathering. So, I am wondering, what would be a more realistic panel line/panel technique; 1) paint panel a darker color, lighten the center of the panel, then use a tech pen for the panel lines, or 2) paint hte panel the required color, then airbrush the panel edges and lines to make them darker than the panel, then tech pen.

Which would look more realistic? I know that with tanks, dirt tends to settle in the panelines, but in aircraft the panel lines tend to leak. Which would be more appropriate for mecha?