Complicated colour shifts, such as the patterned gradient of the yellow feathers, are difficult to paint and can become confusing for the viewer if you’re not careful. So I create a separate version of the red feathers on a separate layer, then use Curves to change it to yellow. A Layer Mask on an Eraser brush can be used to manage the transition.
As I go, I carefully add detail into the background. I want the hillside in the background to be rocky, but not interesting. I want the explosion to be energetic, but not distracting. I don’t add all the detail at once because alternating between the character and the background helps me see problem spots.