Opening and closing documents is not a cumbersome activity, but when you have over 200 students it can be a pain. Throughout this year of training teachers in google drive and google classroom during 14,000 chromebook rollout the issue of saving time has been a carrot to help teachers buy in to the program. So far the favorite tip has been that of the great eye.
In google drive, rather than double clicking a document try a single click. In the upper right of the page are options to get a link, share, remove, and THE EYE. Click the eye to preview a document. Scroll through, mark the grade in your gradebook, then click the arrow on the right to get to the next document in the folder. You cannot edit or comment in this mode, but if you want to comment in a few documents click on "open" at the top of the preview, do your thing then close that tab, preview kept your spot. Since it doesnot completely open the document, things open fast.
If you have assigned something in classroom, open the assignment folderand go through the preview of documents. The titles (with student names) are in the upper left, all documents for a class are in the same folder. For those who enjoy comparisons it is like flipping through a stack of papers like the good old days except it is minus the loss of trees and the process can be completed at any point to show that assignments, especially writing are iterative and nonlinear, that students should be constantly working, editing, and rethinking as they work toward the mythical final draft.