how do I remove the old trailing arm bushings?

Use a torch, heat until you get just a hint of smoke, then pry out.

I don't know what you're planning on replacing them with, but I would advise against the poly. They don't fit very well, and squeak unless they're well greased. Check with PMBPerformance and see what Eric has available.

I use a gear puller and press the shaft beyond the bushing. Pry out the bushing and push the shaft back the other direction to remove the other bushing.
I don't think you are going to pry out a 2 inch bushing with the shaft in place. Other method is use a press to push the shaft.

I used a press and pushed the shaft all the way through the trailing arm.
Easy peazy lemon squeazy.

Quick, easy, smelly ...

cook that puppy out. stinky smokey