I'm much more a fan of manual painting of all the feathers. I've seen some people go very far in this, going as far as painting each fiber of the feathers, but overall just painting the feathers individually, thne highlights gives a much better result than drybrushing them. I tried the drybrushing, I didn't like the result at all, same thing with the razorwing feathers.
You decide yourself whether you go for quality or just a fast & easy result.
Overall, the people who painted the feathers correctly get much better results.
I'm a competition painter, the drybrushing technique on these doesn't work like it does work on other stuff. I've painted marines, I did achieve good results on wings with drybrushing, but not on these scourges or Razorwing wings.