I would stop before you get into the rendering if you want to do a bunch of quick studies. Most of the work is placing everything correctly and proportionally, so once you have that on the page move to the next one. After you get your practice in and you have the desire, you can pick one or some to render and finish.

Nice job! I think you did a good job at capturing the "feel" of the face. You drawing looks recognizable as the subject of the photo, and that can be difficult! I do think your drawing looks somewhat flat. That may be because there is not a lot of variation between the darks and lights. Squinting at the photo makes it seem like the cast shadows (from the nose, ear, lips, and under the chin) are as pretty much as dark as the hair and probably darker than the eyebrows. The highlight on the cheek is barely visible in the drawing. I think a broader range from light to dark would have give more depth to your drawing. As for training more quickly, consider how you might be able to focus your efforts. Instead of doing the entire project, select a portion to do. That might mean just doing one part of the body. That might mean doing the sketch and then copying that sketch multiple times to use as a starting point. That might mean not trying to get certain aspects entirely correct so you have time to focus on other parts (such as not worrying about proportions so that you can focus on rendering the forms). I've seen some good advice about accepting that you are going to make bad art while you practice. The point of practice is to improve your skills, not make something that looks good. You might find value in a shift in focus like that.