Just attended an heirloom feathers (and background fillers) class taught by Cindy Needham at the Augusta Maine show. It was inspiring and I started to get the gist of the feathers much better than my many previous attempts. Cindy also has a Craftsy class online. If you like to learn from books I think Harriett Hargrave is the best. As we can see there are a huge number of resources to learn. The key to it a ll is the practice.