Here are instructions to publish a quiz after the long answers (or other questions) that needed additional grading after the student submitted a quiz.
Log into your course, select Activities, then Quizzes.
Scroll down, click on the triangle beside the exam you want to publish, and select Grade.
This will result to something similar to:
Next, you want to select ALL the students (if you have more than 20 student, make sure you change the default setting of 20 per page to 50, or more), as shown in step 1 below. Then click Publish Feedback as shown below in step 2.
If you have a grade item associated to this quiz, you can also publish this in the Assessment tab of the Quiz, as indicated below:
These two methods will publish your quiz results.