you're talking about jacking up the car, squirting in urethane while everything is still together and on the car? It could'nt hurt, but bet on the car being debilitated for a couple days while it "sets."

I just took off the trailing arms and installed new bushings. Not particularly easy, but guaranteed to work. :dunno:

:edit: total cost ~$40 for bushings, total time spent probably 6 hours with lots of dremel/chisel time.h: