Marking on a computer is less preferable to a red/green pen (or many more colours if you teach in the primary sector) because it involves closing and opening documents, reading on a screen and typing. However online marking can save a tremendous amount of paper...
I have discovered an application that can be added to Google Drive that allows you to highlight text and record verbal feedback. It is called Kaizena and can be added to Google drive by going to create and clicking on connect more apps. Below are two videos showing written feedback and verbal feedback on a Google document. You can then make your choice about which might work for you.
Written feedback in Google Drive
Verbal Feedback in Google Drive
More and more schools are under pressure to reduce budgets and printing can often represent a large proportion of the budget that can potentially be cut. Online marking is getting easier to do and with students using cloud based services to complete their work it has the potential to be more common for teachers to provide their marking and feedback through a computer screen.
In my opinion the Kaizena app is not as easy to use as it could be and until it improves you may still need to type. If that is the case there are ways to improve the speed of your typing.
This site gives you a random assortment of words to type and records your time and the number of errors you make. If you are competitive this might work for improving the speed and accuracy of your typing.
This one costs money so probably only an option if you are really serious about improving your typing speed!
You can also get a number of apps that connect to google's internet browser chrome.
Please let me know how you get on with online marking and feedback.
Technology for Learning Lead Practitioner