In The Fox Girl, the original image of the masked girl in the field was not as separate from the background as I wanted. I selected her and did a levels adjustment on her then continued with the duotone composite.
Sometimes it helps to select a bit of the scenery and composite it over the element I'm inserting in order to make it look more like everything belongs there. I did this with the weeds/brush. I did the same thing in Radio Flyer.