Okay. Here's a fly tying tool that you might not see discussed much -- an iron.

Just use the iron to flatten curved feathers before you tie streamers with them. Just be careful so you don't get the feathers too hot. You can put these feathers between 2 lightweight cotton towels and steam them if you want. Flat feathers are easier to pair, and to tie in on top of the hook, when you're tying 2 or 3 of them together.