The sketches using blocks of tone were quick and in that sense easier, also I blocked off daylight to a large extent for those.
The sketches using lines and spots took longer. I continued to use a spotlight which creates a less fluctuating shadow and decided to ignore any change occurring as a result of variations in daylight. This made it simpler, though it is surprising how difficult it is to gauge exactly how light or dark any one area is.
Make four distinct grades of tone using four tools and lines, hatching and spots. Daylight was so soft it only made two tones. I added a spotlight to create a bit more variation.