The standard workflow for creating morph targets in other 3D apps is to export the body part As Morph Target (No World Transformations) under the Export Options.  Export your Wavefront OBJ, import into your app and deform the mesh to your specifcations.  Make certain all vertices remain intact.  Export again as a Wavefront OBJ, but this time, within Poser select the body part of your model, open the menu under Object in the taskbar and select Load Morph Target.  The new window will ask for the new location of your modified mesh, then give it a recognizable name.  A new dial will appear in your Parameters Palette, dial it to 1 and your morph will appear.  This new character can be saved into your library.  Using 3rd party software, you can generate an INJ/REM file for distribution. 

Creating MAT Pose Files and Material collections (MT5, MC6) begin in the material room, and you should become very familiar with it's setup.  MAT Pose Files is a convenient cheat to easily apply textures from the Pose Category of the Library.  It was created several iterations ago and maybe on it's way out.  More and more advanced users would rather use the material room for direct texture and shader application. 

To create either MTL collection or MAT Pose, enter the material room, create your set up, select a folder in the Library under the Materials Category, and click the + icon at the bottom.  We will be prompted if the material collection applies to one material zone or transcends several material zones.  Again, you will be given a selection.  Give it a recognizable name.  This procedure will create either a MT5 or MC6 (MT5 for single zone, MC6 for multiple zones). 

To create the MAT Pose File, open MT5/MC6 in a text editor, change MTL Collection at the top to Figure.  Save your change (don't overwrite the original file).  Go the folder containing your new MT5/MC6 file and change it's extension to pz2.  Transfer it to a new folder within your runtime/Pose folder and that's it.  Be aware, MAT Pose files cannot be applied to props unless they are parented to an actual cr2 figure.  This does not occur with actual material collections.  And sometimes they can be a little troublesome.

BTW:  Just a note of correction, when referring to particular versions of Poser, please call them by their proper names.  The version you are using is PoserPro 2010, not Poser 2010.  This terminology will only serve to confuse, and will only delay help if you have problems with the software.