Some of you have asked what brushes I use. 
Here are my brush settings for Sketchbook Pro.
I have fairly extreme pressure settings as 
I'm pretty lazy and don't like swapping between different size brushes, 
I let pressure handle the change. 
I should mention I have a corresponding eraser 
for each of these listed below: 
when I use a certain brush, I always use the equivalent eraser.
Old pencil/ink brush:  
New pencil/ink brush:  
Triangle ink brush:  
Watercolour/Paint brush:  
I've tried recreating these in PS and Painter but with no real satisfactory results. 
As I use PS for 'post' work, levels etc, I use standard preset brushes.
Hope that's of some use!