Rubrics aren't just about summative feedback, "Here's how you did," they are also a sort of preemptive feedback, "Here's what you need to do."
allow a student to choose the section or numbers they feel best represent their comprehension
Rotate groups of students that get more percentage of your attention.
Teach the students to give the first wave of feedback to each other.
Carol Jago reminds us that it's the students job to correct their errors. In fact, it would be even more powerful for them to identify the errors in the first place using hints provided by you
Develop a key of symbols that you can use in the margins instead of writing in sentences or bullets.
This will require students to translate as well, which embeds the lesson even further.
Sometimes, assignments will take a huge leap in quality when students think someone other than their own teacher is seeing them.
Keep the final grade of an assignment as a carrot dangling until the feedback is read, attempted, and proven. Make them solve some of the problems in the assignment based on your feedback, and trade their solutions for access to their score.
You conference; they write.
Stagger due dates for your classes.
Ask them what worked and what didn't. Model your own comfort at criticism and they will work harder at their own.