Official video from Google on the various grading options available in Classroom. Annoying voice but good content! :-)
Note that the "coming soon" option of downloading grades to a spreadsheet is now available
There are MANY help videos online for marking pupil work. Remember to search for "grading" rather than "marking"!
A huge timesaver especially when marking written work
Enter a comment directly into the comment bank
Open a student assignment in the grading tool.
In the top-right corner, click Comment bank.
Click Add to comment bank and enter your comment.
Click Add.