The add-on has built in Green Tick and Red Cross for faster marking. You can also pop-out the window for more detailed annotation.
Chrome Extension
You can apply an annotation canvas to the entire Google Doc to allow for easier annotations and marking. You can also adjust colours and save your annotations to the Doc in one click.
This extension is still under development but is available now to experiement with a use. Please feedback any problems or issues you find and we will aim to address them as soon as possible.