You should try the welding trick. The arc is about 10,000 deg's. So there can be a lot of shrinkage on the cold bushing. As for cutting with a torch it helps to preheat the bushing on the inside till it starts to glow. Then you can pull the torch back a little bit and hit the oxygen lever to blow the orange hot steel away. You'll be able to see when you're close to edge easier and just blow the red hot steel out. Gouging with an air arc you can see pretty good but it takes practice. Easy to make a mess if you've never done it. Very loud and a big shower of sparks though. Need to have a clean cutting tip with a torch especially the center hole so it's a nice straight cut. I've left a little bit of the bushing and then used a chisel to turn the bushing and it came out.