You Tube is a great source of learning for almost anything. There are some good videos appearing for bridge learners. The two videos below will teach you about Blackwood and slam bidding. Please let me know if you find these useful. If you are new to my site - this is not me! I don't believe in reinventing the wheel when someone else has already created a useful teaching video!
As well as being a Bridge Teacher I have been a Training Manager, an Air Stewardess, I have hiked down the Grand Canyon and held a live "carpet" python.