Ok so to make it easy if you used Blender, then you can as well rename the material regions there , add materials or merge them. your model mostrobably is triangles ! this can also be changed in blender, with caution as it could cause very bad shadow edges. click Mesh and go into edit mode in blender, hit Alt-J, this will make the mesh tris to quad, make sure to mark " Compare Uvs " else these might get messed up. If you wish to make groups to rig the model in Poser make sure to Remove Doubles in the Transform tool on the Left of Blender before you make tris to quad.

these steps will help you to get a better start when importing the mesh as Obj into Poser