I like to use a dark gray or brown wash to highlight my panel lines. I have even used a fine tip black pen which is drawn down into the panel line and then use a rag with alchohol to wipe most of it away. You just want to leave a hint of dark down in the line to make it stand out a bit. Less is more when it comes to weathering so be subtle. Good luck.

PS- on a dark airplane you may consider a wash of a lighter color