Hey Estevao -this post is for you. So sometimes I want to paint something that is complicated - and it's not your usual figure drawing model that has one simple spot light with lots of clear cast and form shadows.
|not everything is as simple as this.|
This is one of my techniques. I try to treat the form like a topographical map and I use the Photoshop "Cut Cut" filter as an aid. Sean Cheetham does something similar - but he used the "Paint Daubs" filter. Find what works for you.
The middle on is SUPER simplified. I like that a lot. And the one of the right is more realistic - if I want to bring it closer to a photo finish.
Of course - it's good to be able to paint without the aid of the computer. So when I paint live models - I don't have a crutch and I'm able to put on the filter with my mind.
Take care man and draw well!