When it is time to correct all those documents and you find yourself constantly typing the same comment over and over, there are a few things you can do to save yourself some time. The shortcut for inserting a comment in a Google Doc is cmd+option+m, it may only save a few seconds at a time but they will add up. Another time- saver would be to create a document with frequently used comments, then you could copy and paste, (cmd +c (copy) cmd+v (paste)), your comments instead of continually typing the same thing again and again. Below is a video from Caitlyn Tucker that will show how to add "shortcuts" that you can create in preferences under your tools tab in Google Docs.
I hope these were helpful.