If you find yourself in a wrestling match, then every time you go to change your duvet cover, you must be doing it wrong. Instead of shaking your duvet in cover and wrestling with only a hill landscape, try to flip the dowt cover inside the first inside. Lay the dutt on the top of the inner cover and, using the safety pin, pin the duvet and duvet cover together on the top two corners.
Next, push the duvet through the open end of the cover, feeding it until it is right-side out. Give a nice shake to take it out, then reach in and remove the safety pin. Easy.