I agree with Kerry Livermore's method. I used a pair of (very) long nosed pliers, and two screwdrivers. The first screwdriver, a large one, i used to "take over" from the pliers, and then, with the belt held by the large screwdriver I used the smaller screwdriver to gradually move the belt along the brush spindle.
Dyson's suggested method is, in my opinion, impossible without a special tool of some kind.
david,wallasey, June 2010