4. Set the amount of blur, the angle and thinness (in Painter). Since we've outline the whole wing, we're barely going to blur it with a setting of 1.79
5. Now freeform SELECT the wing again, but this time only select the outer extremities of the wing. Now Motion Blur it again-- that's why we went easy the first time!

6. You could depending on the result you want repeat the process again with just the wing tips...

7. Do the other wings--  Make sure you only freeform select what you want to blur...