Use either a small hole saw to cut the rubber, between the inner & out bushings, or drill a series of holes in the rubber, using a drill bit. Once the inner bushing is removed, the outer shell can be chiseled. It's easier if you have a reciprocating air saw; slicing most of the way through the wall of the bushing makes it easier to collapse, using a chisel (or screwdriver), after which it should basically fall away from the swingarm.
Be forewarned, any powdercoat that gets on the swingarm eyes will make it virtually impossible to install new bushings. The masking has to perfect, to avoid major headaches came reassembly time.