This is a perfect example why I try to include 2 files - this is so detail packed my god.
I like to use the "no scar/detail" one for filling in his scars or clothes, since I use the Paint Bucket Tool. This way it's much easier to fill it in, instead of going in and filling between his scars or even paint it all by hand.
Coloring usually takes me around 10min max.
As for his hair - you may noticed that in the "final" Linework, there are no separate strands of hair. That's because I personally like to draw them just with light and shadow.
Of course you can color and shade how you like it! But That's the way I use the Linework (: !