The hairy old chestnut of "Forward" slips. No such thing, your either side-slipping or your not. I did make a point of watching this all the way through, I find this series pretty hard to watch. He did not mention anywhere in the Vid about "Forward" slips, just side-slips and skidding turns.
His side-slips I agree with, a good way of losing altitude/speed. I do not agree with his skidding turns, sure way to depart from controlled flight. With those places he demonstrated skidding turns he could have turned balanced without risk of tip strike. My advice would be NEVER do a skidding turn, any circumstances.