*Lie duvet cover flat on bed.
Lie duvet on top of it but half way down.
Take RH corner of duvet in hand and put inside cover.
Hold on to RH corner of cover and duvet.
Repeat for LH corner.
Hold both corners and shake*.
Cocktail's method works for me too. The important thing is to show the duvet no fear. They can smell it if you do. 