I have noticed that when I study speaking french in my dreams or while I meditate I can remember a huge amount of information way more than in a real life situation.
My brother however did have a dream after he was drawing but couldn't get the water of the flowing river right. Then as he napped he dreamed he saw the river turn to a grid explaining perfectly how to shade water. And he did and it looked quite good.
In this case it almost seems like the brain made up a method of drawing based on its previous sightings of water without my brother ever having to practise it, I think it's because deep down our unconscious minds are the real masters of reasoning, not effected by emotions or desire but purely by past experience.