Here's a shot of a large river painting I've currently got on my easel. Making good progress on it I think. Pretty much only painting a few hours a week, so I do move fast on it when I get the chance.
The idea for this one came as I was running along the trail by the river, and noticed this spot with some really deep areas and such clear water. I could tell there were large rocks, but also just a lot of depth that I thought looked really interesting. I wanted to go large with it, to really pull the viewer into the water and the mystery of what might in there.
Below you'll see some other shots of how I started this one. I decided to begin with a color wash thinned with solvent, because I needed to get the whole canvas covered quickly and the drawing worked out. I don't usually start this way, I often will draw first with charcoal, or maybe do a raw-umber sketch that is thinned with medium or straight linseed oil. The problem with that is that you can end up with an adhesion issue, because you are adding too much oil to the paint.
But here because there was so much to cover, I went with solvent out of necessity.. but it worked so well I thought, "Why don't I always just do this?" Solvent will evaporate away. I have heard that some solvents might leave a film on your painting, so I think that's why I shied away before.. but this is the base layer so who cares if it leaves a film? I'm covering it.
It's so much easier to cover the white background, and then just use more solvent with a brush or paper towel to draw in the major shapes.