Great lesson! But for a more complex drawing of a had this might help http://youtu.be/yAwVyqxOvlc
I just watched ArtPasswork's video linked above. It's a review of a couple apps and a good hand reference one. I'd take a look. Also a good source to practice drawing hands is to google (or as we used to say "look up") sign language images. They might always be the most practical, but you'll get good poses you might not think of to practice with.