My male buddies always look at me weird when I complain about drawing breasts. It's always, "You have some, why shouldn't you be able to draw them?"
It wasn't until I snapped something along the lines of "Look I don't stare at boobs like you *ssholes do, so shut it." that I realized that was why I was having trouble. People forget you draw best what you see best, and not a lot of people spend time studying boobs. Enough tangents, this is a really great tutorial!