A good way to approach a drawing is to first draw in as true proportions as possible, then make a second drawing from the first. This time just drawing the essence of the first, omitting stuff. Simplifying is easier that way, since we no longer look at the original reference but already a ‘version’ of it.
If using a photograph, you can do the same thing. Your individuality will go into the drawing and later the painting, which is what you want. You can always check your changes with the original for accuracy or perspective, but you are essentially making a free interpretation of the picture rather than slavishly copying everything you see in the photograph.
I find that while it also works when painting outside, it is less practical because of the time factor. Light is changing rapidly and it’s difficult enough to do one drawing. It takes many hours of plein air painting to sort of develop the ‘instinct’ of what needs to go in and what can or must be left out! Put in the time!
A drawing or painting is often more interesting when parts of it are left unfinished. The detail and finish in the other areas will have a bigger impact and stand out more.
Ultimately, my goal in painting is beauty as oppose to verification of truth. Generally, people don’t put paintings up that are ugly. I know there is art for all kinds of reason and that’s just fine, but for my art, beauty is pretty important!