One of the aspects of Alvaro Castagnet's paintings that I like a lot is the sense of haze that he creates in his street scenes and kitchen action paintings. As per my previous rant, you will find nothing in his book that actually explains how he achieves that soft steamy smoky effect.
So I decided to explore myself, creating an imagined industrial landscape in my watercolour sketchbook. First I applied Chinese White watercolour, as mentioned in Mr. Castagnet's book. Didn't like it. It partly lifted the original colour. And it was dull and dirty-looking. I tried to spray some water onto it and lift colour. It looked even worse - like water after you've washed the dishes. Not pleasant. At that stage, I had nothing to lose, so I picked up my pastel set and applied a few dashes of colour and a thin film of white, which I rubbed slightly into the paper so the strokes wouldn't be as obvious. Then I sprayed pastel fixative over it. It no longer is a pure watercolour, but I quite like the result. I might try to use that in my current project.