I have painted many still lifes over time, and I like to approach the genre differently at different times. Because it's not always possible for me to paint at the same time each day (for uniform light), I sometimes "practice" the subject by using other media that are quicker, less complicated and more convenient to use. The above drawing is a study made using oil pastels. The size is very nearly one-to-one relative to a painting I'm working on so this is a especially relevant "rehearsal."
Each time I look at the still life motif, I get a better understanding of the relationships between the objects. And I enjoy redoing the same motif again and again using different media as I "learn" the features of my objects. It's very similar to rehearsing a piece of music. Studies like this are unfinished. I am not going back into the drawing to tidy up each loose end -- and yet I like the "unfinish" of a study and find that it has a charm all its own.
I honed in on just the condensed milk can in this drawing made using water soluble crayons. Each medium has unique characteristics. By making lots of drawings "around" the motif, I learn more about what I'm seeing -- I learn to examine the "spaces between spaces." And all of these forms of practice enlarge all one's skills.
Whenever you are observing things closely and recording your perceptions as carefully as you can, you are learning. Whenever you are drawing you are learning. Whenever you are looking more and more closely, you are learning. And I want to be often learning.