As long as you are doing this because you are going to re-case color the frame,,then don't be shy about using heat on the frame in that area to help unlock the bushing from it's seat.

The frame will go through an annealing process before polishing it up anyway before re-CCH. That'll be around 800/1000F.
Then it'll hit 1400F+ when re-CaseColored.
Some xciting heat now won't hurt it. It won't turn to a pile of goo.

Turn up the heat,, turn out the bushing and get it over with.