There are mainly 2 ways that motor brushes can be fitted
1) screwed onto the outside of the motor
2) the brushes are fitted up a slot and held in with a plastic barb
(version 1) undo the screw remove the old brush, remove wire attached to brushes
screw the NEW ONE INTO PLACE and repeat for the remaining brush.
when brushes are secure NOW is the time to RELEASE them free of the brush holders by bending back the tab on the side of the brush holder. Reattach both brush wires
(version 2) remove the brush wires now with a short stubby screwdriver and a stiff piece of hooked wire insert the screwdriver up the slot and behind the plastic barb, press enough to make the barb clear the slot, holding it in this position hook the brush out, if stiff you can use a thin pair of long nosed pliers to pull out remove old brush insert the NEW BRUSHES until the barb holds them in position now is the time to RELEASE them free of the brush holders by bending back the tab on the side of the brush holder. Reattach both brush wires
wirecutterman, June 2008