Here's another video tutorial from our book How to Draw. The book experience has about 10 hours of videos like this one. More about it here: http://www.amazon.com/How-Draw-sketching-environments-imagination/dp/1933492732/ref=sr_1_1?s=books&ie=UTF8&qid=1394760290&sr=1-1&keywords=how+to+draw+scott+robertson
And here: http://designstudiopress.com/product/how-to-draw/