There is now a way to give "completion points" for work!
In "grade by question," place a check in the question that you want to grade. A box will appear on the right that will allow you to input a point value. This box will automatically fill with the maximum number of points.
Scroll to the bottom of the page and click "Grade Question."
This will open the question and will prefill that score for all students who have attempted the question. If the question was left blank, the score will also be left blank. I just scroll through that page quickly and look for any *odd* answers (answers like "cows go quack" or "IDK") change these to 0s.
Then, at the bottom of the page, click "Save All." This process usually takes under a minute for a class of 30 students.
To grade the next question, click the "back" arrow in your web browser. This will take you back to the question list, where you can select another question and repeat the process. To maximize your time, you can select up to five questions at a time.