Firefly renders in software, not hardware. You can get it to use more than one process and that will speed up renders of large scenes.  Otherwise, you have to start considering the fairly useless amount of information you may or may not be sending to the render engine. Most of the time, Poser models feature textures that are larger than needed, especially if the image will remain static on screen at standard resolutions.   For animations, if an object doesn't appear directly in front of the camera for an extended period of time, textures larger than the screen res is a waste (for example, a lamp post in the distance doesn't need a 2048x2048 map if the final output is 640x480).

Decreasing texture size in models in the distance will speed things up.  Some creators provide LOD models (level of detail) models also, so consider using lower res meshes where appropriate, which will speed things up also.

I hope that helped. If you need more help than that, you can try contacting Smith Micro technical support or ...continue asking here I guess.