Martins shading panel lines using a lead pencil is probably the easiest way to achieve this effect. Remember though, Marc, any technique requires practice. Read the different methods, in the features pages, if you have any questions the authers will be happy to answer them, either in the open forum or in a PM.
Pre-shading is actually used for a different purpose, although some modellers do use it instead of panel line washing. I also have an article on this subject, in the features pages
To pre-shade or not to pre- shade I use pre-shading and washes as part of my weathering techniques.
Best of luck with your efforts.
Mal