This picture was taken by a friend of mine in St Augustine Florida, Nancy Vail, who lives on the waters edge. I call this Vails' View, since they see this first thing in the morning. This little island is a rookery for birds as well and a channel connects the property to the Matanzas Inlet. She has invited us to stay many nights there so I know this scene well.
The first thing I like to do is break down the scene either in my mind or in sketch form, into a map so I know where I am trying to arrive in terms of the placement of highlight and shadow, warms and cools, and composition lines.
Remember , you are working around the color wheel (see the left side) so as you move down the cloud toward the purples and away from the yellow, you may get a green if there is still too much, or any yellow in your mix, so as you move away from the orange into the purple shadow, remove the yellow from your brush and add red, use pink and add blue slowly.
I just keep glazing in, adding small amounts of extender with carefully selected mixes of purples.
Extender is something you only use small amounts of, whereas glazing liquid you can use much more, but it dries faster too. You can use both simultaneously to both thin and extend open time. This allows for multiple and sumptuous glazes one on top of another. It is important though to let each coat dry or you will get a chunky surface to your painting that will not be attractive to look at.
Here is the final result of multiple glazing, I still need to add some color to the area above the treeline, that will come next.
Below: The final tweak with some deepening glazes added to the water and a few extra strokes to the marsh grasses.