This is a 3-part tutorial that can be summarised into creation, refinement and placement of the low poly-poly feathers.
The feathers with NanoMesh technique is something that works really well when you want to create lots of feathers to cover a surface. One of my eBook guides on creating feathers describes a variety of construction methods including a more realistic approach using FiberMesh. However, the resulting mesh will have a high poly count and every duplicate of the feather will increase substantially the polygon count.
The NanoMesh technique, on the other hand, allows you to play with texture and transparency to produce a high level of detail while preserving a low poly count.
The process is very simple and it uses custom insert brushes (IMM) and NanoMesh to distribute and randomise the placement of the feathers. This tutorial will show you how I created the feathers for this illustration: