I start landscape paintings either with photos, with rough, flat sketches from my imagination or with both at the same time.
Here I show the cropped picture of a current digital artwork. Initially, structures such as branches in the foreground (A) have only a slightly greater sharpness due to the firmer brush pressure. In the next phase (B) I already worked out the possible end result by painting the foreground and background simultaneous(!) with a suitable brush.
All areas of the upper part of the image (B) were executed with the same brush: "Oil Brush, Bristle, Medium". The simulated depth of field results only from different brush pressure values.
This technique result in a natural variation of the sharpness between foreground and background, without sketchy lines or blocks - for the benefit of a semi-realistic style.
Adjusting lights and shadows for a planned draft of an abbey scene. I'm working with Corel Paintshop Pro here, but apart from that (and Photoshop) there is a big competitor for the task of preparing light effects: Affinity Photo. See this screenshot: