I used coloured pencils with lots of layers to get the effect.
The little bit of roof you can see at the top right hand corner must be at least ten layers of browns and greys. After a while the layers build up and go oily, blending with each other.
I then did a bit of scratching with a a scalpel to roughen it up.
It's amazing how the same tools and a few extra tweaks can give such a different end look, isn't it?
I don't go for quite so many layers, three or four tops, though to get the "shiny" paint effect on racing cars, I will burnish / smudge with a paper torchon, a cotton bud, or even my fingers. An off-white or payne's grey pencil can be used to similar effect.
BTW, I use a mix of Faber-Castell "Albrecht Durer" and Bruynzeel "Design Aquarel" watercolour pencils, plus a smaller range of Faber-Castell "Polychromos" oil-based pencils, usually on Daler Murano pastel paper. I prefer paper with a bit of a "tooth" to it.