Scott uses a photo of the Grand Teton to discuss how he developed his idea into a larger painting.
Journaling is key to idea development.
The difference between the photo and Scott's initial study is significant. The difference between the photo and the final painting are even more pronounced. The message is simple: the photograph and the scene itself are only a starting point. It is up to the artist to find a compelling motivation and develop that into something of beauty.
Your thoughts will develop over time with constant repetition. Words, sketches, gestures, studies and constant evaluation and iteration are the key to success. The really great thing about this approach is that it limits wasted effort. The biggest waste / disappointment is a failed major painting. Better to fail on small incremental steps early in the process. Study / solve your problems on a small scale so you have confidence in your approach as you work towards scale.
Journal your ideal process for developing a major painting.
Identify the points of iteration and review.
Commit to following the process and revising it as you gain experience.
Drawing or Painting Journal.