If you slice off most of the vane with a Stanley knife, you'll be left with the foot of the vane left on. I use a wood chisel to remove that last part.
Not the cutting edge, as that can dig into the carbon. I place the back of the chisel flat onto the shaft and push the chisel along the shaft so the side edge of the chisel moves at an angle to the shaft( 70 deg ish as opposed to 90 deg) that pushes the foot off to one side as it moves along the shaft.
The action is a bit like sharpening a pencil with a knife, but the flat back of the chisel blade, slides along the shaft while the side edge forces the vane off. I make sure the chisel blade stays flat on the shaft as any lifting of the trailing edge causes the lead edge to bite the shaft.
If you can hold and support the shaft in some way, the chisel can be held as if draw filing using the back of the chisel on the shaft. That is safer, specially if the glue doesn't break off on the first pass.