We had an intimate class...but fun and productive! I think this class is most helpful in showing you how much you rely on the photo or not. That alone can be so instructive. We talked about how the "bones" of a painting appeal most to artists, while the "skin" seems to matter more to the viewer.
I used this photo for my demo.
After gazing at the photo for a few minutes and analyzing it well, I put it behind me on a desk (where I couldn't cheat and sort of 'see' it--that's just too tempting!) I painted one pass over the paper to record the memorized shapes and colors and arrived at this:
It's painted using PanPastels on a piece of yellow Pastelmat paper, giving it a lovely soft focus, slightly blended look. I felt the colors were creeping into the sunset hour, so I pushed it that direction, adding a hint of color to the sky suggesting the setting sun is off to the right. This came about as I painted, not as a result of the photograph. I checked the details more as I progressed, to find the various cloud shapes when needed, but freed myself to make a painting out of it that contained my own ideas.
I hope you'll enjoy using this technique yourself.
Have fun, gang!