"What methods are other people who have switched to OSX for most of their programs using to still be able to use Poser 4"

Poser 4 runs fine in Classic mode under Mac OS X, despite not being formally supported. Poser was never a "well behaved" OS 9 application anyway, and that makes it an even quirkier Classic citizen. But it works. The only oddity I've encountered is that switching away from Poser during a render is "awkward". It tries hard to pretend you're running OS 9, though I can usually manage when I fiddle. (And Poser won't refresh the window, if you switch back, until the render is done.)