How to get rid of sticky rubber (remains of rubber bushing)

Replacing old rubber bushes for polyurethane - option 1 which I avoided was removing the entire rear axle (a lot of hassle removing the brakes and everything else) and burning the old bushes out. Lots of work, messy, and nasty smoke.

So decided to do it with the axle still on the car, drilled around the centre bit of the bush, this got rid of most of the rubber with a hole cutter that's fractionally smaller than the casing, but now left with almost a layer of rubber "bonded" to the outer metal casing. After trying various different tools and attachments I've ended up now with a sticky melted layer of rubber, a couple of mm thick in places, and no amount of scraping seems to get rid of it.

Is there something I can "soak" overnight to dissolve it to be able to easily scrape it off? I know diesel attacks certain types of rubber, but ideally could do with something pretty rapid to get rid of it so I can get the new bushings in ASAP.

Did the original bush have a metal outer sleeve? (I know, just worth a check)

A drill flapwheel is pretty good for cleaning up that sort of thing.

If it's melted and moving about you might be able to get it off with a solvant like Nail Polish remover or rubbing alcohol (IPA)