OK, a couple of people asked what i did exactly:
used 4 x Gundam pens, 1 x brown ink Gundam pen, 2 x staedtler Lumacolour black Permant pens and s blsck artline permanent marker.
The panel lines are a mix of the thing and thick pens that i had. i used the thicker pens to colour in areas of solid black in certain area, most nooticeably the recessed circle areas and the sides. i then used the thin pens to quickly squiggle a stain someone then smeared it with my finger. Did this with the brown pen too. Also made what looked (To me) liek grease or rust stains using the thinner pens, usually trying to have them come off something, be it a panel line or one of the random lumps the falcon has all over it.
the darker black 'stained' areas i coloured m,my finger with the permantn marker then quickly rubbed it over certain areas, mainly round the rear engine circles and behind the Sensor dish. did this a few times. went back in and added rust witht he brown pen over those areas too.
Thats it! Not too hard, just takes patience. Oh, i did the fighter too, Ill have to takle pics of it sometime. panel lined the X and B wings, am trying to decide if Ill do the interceptor and y Wing or not...