A picture might help a ton here. I had a wbs core and there wasn't a way to open it.. as it was a solid piece.
your core tubes break off?
id get a thin putty knife to start with, and pick a corner to start love tapping it in between the two 1/2's, work the putty knife down one side, as it starts to separate use small screw drivers to pry it apart slowly. working your way around the outside of the core.
Split it open a little on the seam. Spray brake clean in the opening. Pry a little and repeat brake clean as needed.