#1 I usually draw directly on the pencil sketch but this time I decided to make a clear line art. I used a hard edged brush in a multiply layer.
#2 In a normal layer below the outline I added colours, using a hard edged 100% opacity paintbrush.
#3 I added some textures on top of the coloured layer and changed the blending mode to overlay. I used a noise texture to make the image less sterile and CG like. I set this layer's opacity to 50%
#4 I created a new soft light layer to add some shadows with a black, hard edged paintbrush and a soft edged 15-40% opacity airbrush.