German Short rows work with any yarn – no matter if you are knitting in the round or flat. It’s just a general technique to avoid holes and gaps whenever you turn your work around in the middle of a row and continue in the other direction.
Norman at Nimble Needles has very comprehensive tutorials and videos on german short rows and\or watch the step by step tutorial by Wendy Pool on German Short Row Heels.
Norman from Nimble Needles has a great tutorial on german short rows, it includes video and written instructions – click the image to view this page
Wendy Pool How to work german short rows for socks. To view full screen click the full screen image at bottom right of video 
If you cannot see, click the play button to access the video and then the image will be visable.