Dumb question, if you take the whole thing out with an air chisel, how are you gonna press a new bushing in? Air chisel won't help you there at all. Just pull the bolt, drop/pry the arm, and light up the rubber bushing with the torch. In the end you're left with the outer shell still pressed inside the beam, but that's exactly what you want. Then grab a set of polyurethane bushings, grease 'em with their provided lube, install poly bushing into old shell, slide new inner sleeve in poly bushing, pop the matching poly ring on the other side, slide the beam back in the bracket, and reinstall the bolt. No presses, no axle removal, none of that mess. And yes you will likely need a long prybar and a come-along or at least a beefy ratchet strap to help you pull the beam back in the bracket. It's not exactly a fun job, but it's not rocket science either.
Also I disagree with the suggestion to use a jack under a prybar - use one or the other, both together can send stuff flying. And watch out for the beam springing down from the bracket when you pull the bolt at first, it may or may not do it, but just in case keep bodily parts away from underneath it. You can pretension it somewhat with the come-along before puling the bolt out, then gradually loosen up the come-along and let the beam assume its desired position.