I always paint from the background to the foreground. Here I'm blocking out the sky and cloud shapes. I work with a 1/2 inch flat brush. In order to get smooth blends, I use an old Winsor Newton 3/8 inch chisel point brush that has been thoroughly abused. This old brush is used to 'scrub' in the paint using very little water - the drier the better. When blending in this manner, it's best to go from dark to light. The clouds are painted with this scrubbing technique. Once all the values are working and the shapes are correct, I may use a Winsor & Newton series 7 size 0 sable brush to define some of the cloud shapes. I do this sparingly so I don¹t ruin the nice blends from the dry brush.