Spraying and back-brushing rough texture
Rough-sawn and grooved shakes are sprayed and then back-brushed, so the coating reaches into every groove instead of bridging over them. Modern shakes are usually left undressed with a rough, corrugated surface, and a spray gun alone lays stain on the high points while the low ones stay dry.
Brushing works finish into wood better than a roller or a spray, especially on the first coat, so the crew sprays a section, then follows straight away with a brush to push the wet stain into the grain, the butt edges and the gaps between shingles. On a semi-transparent system the second coat goes on while the first is still wet, which only works when the person spraying and the person brushing move together.
Wind decides the spray days. Temecula sees strong, dry Santa Ana winds from late fall into winter, and stain mist carries a long way in a gust, so on windy days the work switches to brush only or waits.