Itapirkanmaa2 - "The technique seems to be to put the plane into a series of sideslips in order to defeat the lift from the huge wing area."
Defeating lift is something called a stall. Reducing lift is done by simply lowering the nose not side slipping. Sideslip is done to increase drag - allowing for a rapid descent without building up speed.
Here the pilot is done some power off stall turns. It is hard to see if he using slip but the AN would be able to descend like a controlled brick with its massive fuselage presented.