If you're using Ogre3D, then why don't you do add another pass to the material technique that is assigned to the model, as in (suppose "ball" is an Ogre::Entity):
Ogre::MaterialPtr ptr = ball->getSubEntity(0)->getMaterial();
Ogre::Pass * pass = ptr->getTechnique(0)->createPass();
pass->setDiffuse(1,0,0,0);
pass->setAmbient(1,0,0);
pass->setPolygonModeOverrideable(true);
pass->setPolygonMode(Ogre::PM_WIREFRAME);
This will add a red wireframe that gets drawn over the existing material. And if you just want a wireframe, not a wireframe on top of the current material, just substitute "getPass(0)" for "createPass()"
Or, if you would rather do it in the .material file:
material general/wireframe
{
technique
{
// first pass
pass
{
polygon_mode wireframe
...
See:
http://www.ogre3d.org/docs/manual/manual_16.html#polygon_005fmode
http://www.ogre3d.org/docs/manual/manual_14.html#Material-Scripts